Games that have fallen off for me:
-Catan
-Ticket to Ride (my family played this so many times when they got it that the thought of even looking at the box makes me want to puke)
-Cosmic Encounter
-Eclipse Second Dawn
-The Resistance
-Villainous
-Star Wars: Outer Rim
-Descent and Imperial Assault
-Star Wars: X-Wing

For Heat I created 3D printed sub ins for the various road rules and just custom create maps with them

Heat couldn't even give you the six cars. They drip feed you 1 car at a time per expansion.

Great choices mostly :) For me i have especially 2 games that come to mind

Darkest Dungeon: I still think this game has some amazing ideas and concepts, the battle phase and how much the rooms change the tactics is amazing, and the city phase is probably the best ive seen in a game with the blocking actions each day. However due to the fact that the game NEEDS the expansions and those never arrived it suffers from it. Backers have since received files so everything can be printed yourself, but getting it in the same quality as the core box and miniatures and everything is something im not ready to do as a project right now. Hopefully in the future it will be possible for me to get those expansions somehow.

Oathsworn: When i first played Oathsworn it shot to my number 1 spot of all time. I was already seeing myself ready to want to run an extra campaign after the first one and everything was amazing. However the further we got the more we cooled on it, and the last 3-4 chapters was mostly due to the fact that now we wanted to finish it. The game had too many ideas thrown in just to be there, which were never used, (Injuries, Event Decks, A lot of Gear, Maps etc. or my personal grievance the secret votes, which was amazing, but only came up like 5 times total). The rules were so disjointed that we had questions about rules on most of the final bosses, as one mechanic might be written in one way on one boss, but then a seperate way on another even though it was the same boss. Furthermore the story became more and more railroaded it seemed, instead of opening up more. And most choices came down to "which token do you get". Finally each place was not explored enough.

Finally i havent played it enough to give a final verdict but my initial thoughts is that Elden Ring the Board Game is a significantly better design than both Bloodborne and Dark Souls the Board Game. (The latter probably being my worst gaming experience ever)

Sad to hear you burn out on Marvel Champions.   I recently decided to start at the beginning and to to play every scenario with heroes from that cycle or prior.  I'll first use the precon deck then once I have tried tried that for all the heroes  will then add a random hero with a deck with a card pool up to that current wave.  I chose to avoid the campaigns because I didn't want be forced to use the same heroes for 5 games.  Hopefully I'm not burned out by the end.

When you mentioned the Dark Souls board game it made me cringe a bit. I so wanted to love it. But I've only played it twice and never again, I should really sell it.
As for Heat, I feel the same way. Heavy Rain I thought it was they brought the chicanes in for both maps. But when Tunnel Vision was coming out and they only had Spain with the tunnels I was upset. Because they're spending so much time making these special things for just one map. It's honestly kinda lame. Also same with the new championship season, they only include the two maps from the expansion and then two from the base game. Although, I do love Legends, it makes the solo game 10 times better and more challenging without strictly adding more movement on them.
Also dice throne. I played a bunch of it and then got burned out fast. Especially after I got into Unmatched instead. So much less random.

I just picked up 20 Strong AND Cloudspire at Gencon this year. 20 Strong has been enjoyable so far, curious about long-term playability. Cloudspire hasn't been played yet, too busy with ES:BOTSE.

I will say, Everdell: Complete Collection is probably my wife and I's most frequently tabled game somehow, but I understand the issues with it. I'm tired of boxing and unboxing it each few weeks

My copy of Isofarian Guard is still sitting in its shrink. I’ve been debating whether to keep or cull it. The way you describe the constant fighting really doesn’t sound like an enjoyable experience in a long campaign. 😂

Oathsworn is the game that fell off for me.  Once you get like halfway through the campaign, it gets so boring.  All of the fights play out the same.  There is no character development.  You barely get any cards to swap around compared to other campaign games.  The whole thing where you lose gear at the end of the fight just to get the exact same piece to replace it is so weird.  The story is really cool and the app does a lot of the heavy lifting and has good voice acting.  I wish they had cut the game down to like 14-16 chapters and gave some branching storylines.  None of the choices you make during the story matter.  You just get a different token or start damaged or not.  It is weird knowing that you will end up at the same place no matter what.  We are on chapter 16 and none of us really want to play the game and we are at the point where I think all of us would play if someone wanted to but none of us bring it up.

Always an interesting topic, its torturous when a game comes out of the gate strong and then has to be abandoned when the flaws appear.

Comments on each entry:
OM: Everdell. Hard to argue. I will defend the big box in that it is an excellent storage solution for the full game with everything, its pretty easy to setup from and pack away, its just that it is TOOO BIG! It could have been done in a way more compact way to save shelf space. I still like Everdell a lot, but I play it less due to being at well over 100 plays already. Rated an 8 but that's down from my #1 all time game.
10.Cloudspire. Played once, absolute garbage game, literally just a contest to see who could remember the most keywords, even if it was streamline the gameplay was totally boring. Rated a 2!
9. 20 strong. Looked like a flawed premise to me, hard passed and no regrets. Final Girls scratched this itch for me and wont be dethroned by other games that are similar.
8. Played once, was nice enough, my reflections were 100% identical to yours.it did look like it would get boring after a while and it was so lacklustre and has never even been mentioned, even by the owner. That probably tells you enough.
7. SHASN. I have intentionally only played this rarely because its clearly the type of game that wears thin quicker. Still really like it as a unique 1-2 plays a year game. Shame the sequel wasn't a hit, I haven't tried it yet to comment.
6. Time stories. I tried to outsmart the market, I figured since the game is not super repayable, I would wait for a 2nd hand copies to flood the market once people were done with it and pickup a bargain. But they kept releasing stuff so it took ages and by the time the started getting sold of the series had gone downhill and everyone said what a disappointment it was, so I just skipped entirely.
5. Heat. Its okaaaay, but its a much worse version of Flamme Rogue which I really enjoy as a family weight game, pure hype by DoW fanbois. Just get the OG.
4. Kingdoms Forlorn: Never heard of it.
3. Dice Throne. Still really enjoy this. I play with my brother in Japan over facetime call and it works brilliantly. We don't take it too serious but we are about equal skill. Disagree that the characters are very unbalanced, the patch notes were pretty minor and games like this are never perfectly balanced. I think playing a tournament would kill it too, games are only fun if you play until your over it and then pack up. Tournaments force you to play to a point where games outstay their welcome.
2. The Isofarian Guard. I don't trust new companies with big box campaigns anymore, I wait for reviews and the reprint KS/GF. Its very rare a great game doesn't get a reprint.
1. Marvel Champions. No interest in super hero themed games, I get nothing from the theme and I find the designs are usually lazy and just to exploit the IP.

Was expecting to see Scythe on this list, you still play that?

For me I would add Ewe Rosenburg game to the list, he always has annoying bottle necks in his game where people race to an important milestone and first there wins.

Hegemony. 10/10 after first game, but game 4 I realised its a total mess that doesn't work as a game at all.
Dune Imperium. Once again cool mechanisms, but I found after 3 games the luck of the draw on the intrigue deck is too influential and cant be mitigated.
Lost Ruins of Arnak. Looks like a lot of cool mechanisms mixed together, but the deck building and WP are very boring versions of those mechanisms and its a dry resource conversion game ultimately. Playable with the characters expansions, but not great.
Through the Ages. Fantastic game with wonderful mechanisms. The luck of the draw on the military cards kills it, too many 3 hour games ruined to ever return to it.
Quacks: Sooo much fun, for 3 games and then nose dived into a repetitive snooze fest.
Pax Pamir. Seemed so intricate and fascinating at first. But after a few games, its just people whacking each other randomly, not because it makes sense, just because you can.
Ancient Knowledge. Fun for a few games, looks deeper than it is, after 10 games you have seen everything and it goes to the sell pile.
Wreck lands Run. Fun mechanisms on the easy levels, but they are not challenging. After the difficulty ramps up the mechanisms fall apart and you cant actually win except by drawing lucky.