the one thing that has always infuriated me about warriors is the trend that female cats either die young or eventually become mothers and fall into the “sweet, laid back, caring mother” personality

In defense of Brightheart: I think her quietness is to be expected. She most likely has a lot of ptsd and trauma from the dog attack and losing swiftpaw. You can't expect someone with a past like hers to be all spunky and outgoing. With a lot of the others, though, you're ABSOLUTELY right in terms of the idea that they are stock characters - a ton of cats are stock characters in wc.

I'm still mad about how they wrote squrrielflight's temporary leadership role. Put simply, the warriors refused to respect her, but immediately respected Graystripe the minute he stood up and spoke. Really irks me.

I'd like a story where a male medicine cat has a forbidden relationship and kits 😊 Not to add to the "Let's have more stories about males" I notice that after writing 😅 I just wish we could let males focus on their kits and family drama

Is it just me, or is Mousefur the only ThunderClan she-cat from the main series who became an elder without having kits?

We also almost never see toms and she-cats just being friends either, which probably doesn't help with the deputy and leader disparity since leaders seem to often choose cats they have good relationships with as their deputy. She-cats and toms seem to only be presented as having either familial or mate relationships, and I vaguely recall there being backlash about Bramblestar choosing Squirrelflight as his deputy specifically because of their mate relationship, though it's been a while since I've read that arc. So since most of the leaders seems to be toms, and toms often only hang out with toms on a friendly or professional basis, they pick toms for their deputies. Note that one of the more prominent she-cat leaders, Leopardstar, was succeeded by Mistystar, which suggests similar ideas, though Bluestar did not have a single she cat deputy (though as you pointed out most of Thunderclan's she cats were in the nursery, elder's den, or were medicine cats during the first arc).

Did not realize how many main stories with she-cats centered on romance and family - surprisingly that even in this time, that is the stock storyline the authors subconsciously choose

this video goes to show how sexism (or any "ism"/phobia in general) can many of times be shown unconsciously and without knowing, with beliefs and stereotypes about a social group rooted so deeply that you can't even tell what you're doing until someone else points to it
i do believe that the erins themselves didn't necessarily mean to write this way, but like i said with deep-rooted stereotypes it's almost hard not to. even then,we can't really know for sure since i doubt any of us here have ever developed a close enough relationship with them to start connecting dots

I'm a sucker for close sibling relationships and they are always blown out of the water when a romance comes along. Like "I don't need family anymore, I have a MATE"

In Yellowfang's case, I think it's terrible that StarClan themselves set off to punish and then actively blamed Yellowfang for falling in love and starting a family by killing two of her kits and giving her one pure evil one that goes on to commit many crimes.

StarClan genuinely blames Brokenstar's entire existence on Yellowfang and the fact she had to 'atone' for her actions by enduring his awful treatment of her for most of his life, then later killing him herself twice just because she fell in love and had kits against the code is actually tragic and terrifying.

Literally most, if not all she-cats who break the romance code in the series are severely punished in some type of way or other while the toms more or less get a slap on the wrist and it's honestly very upsetting.

EDIT: Gonna make a long comment even longer by adding some examples.

Bluestar has a mate and kits with Oakheart as a warrior. She was forced to give up her kits (with one of them DYING due to the authors having her take them out into the freezing cold) because otherwise she would have had to give up her shot at being deputy against Thistleclaw because she was a QUEEN. Oakheart, meanwhile, gets off scott free and gets to keep his position as deputy AND raise his kits.

Dovewing has a mate and kits with Tigerstar 2.0. She is judged harshly and branded as a traitor by her friends, family, her SISTER. Tigerstar 2.0's position as a respected leader remains and the narrative only brings up his forbidden romance with Dovewing as a neutral or positive thing.

Silverstream enters a secret relationship with Graystripe. She is ridiculed by Leopardfur and Crookedstar, threatened by Fireheart, and later dies during childbirth. (Although Graystripe does face scorn/punishment for his rule breaking afterwards)

Leafpool enters a relationship with Crowfeather and had three kits with her. She was attacked by her mentor, has been neglected and bullied by Crowfeather constantly after their breakup, outed in front of the entire Clans by her daughter, who tried to murder her, hated by her kits for moons (even at her FUNERAL Jayfeather had to act up), shunned by her clanmates, had to give up her medicine cat position, and was again in danger of losing her life to Breezepelt. Although Crowfeather faces some scorn and mistrust to a degree, he is overall given another chance and retains his warrior position and gains another mate in the process. And these are NOT the only examples.

On the she-cat's side, forbidden romances are seen as a big mistake, something to be ashamed of, to apologize and to be judged for. On the tom's side, forbidden romances are seen as forlorn, lost chances, something sweet to remember and to move on from, or to laugh off.

I would love a female villain who’s evil for ambition

And a male villain who’s evil because he lost his kits

Squirrelflight not being recognized as the Three's "real" mother after it was revealed they were adopted feels really icky to me. I haven't read Squirrelflight's hope, but I think there's a scene where Hollyleaf runs up to Leafpool, who has literally always been her aunt and has not raised and loved her as a child, first and saying "mom!" (or something along those lines)
And Squirrelflight being treated so horribly by her children when all she did was love her kits.

Having female writers is great but it doesn't exclude the possibility of internalised misogyny when it comes to writing characters

The series started off with a great gender balance. It felt like there was no real difference between she-cats and toms except that she-cats occasionally took time to raise kits. However, the gender divide has gotten a lot worse as the series has went on.

Hell yeah, this is a discussion that the fandom needs to hear and think about. I'll never forget back when someone tried rewriting the series to be "better and realistic" amd made the decision to kill off Sandstorm for man pain.
As far as antagonists go, we have the cats you mentioned, Maple, Misha, Sleekwhisker and Rainflower. We also had Starflower towards the end of DotC but I really despise how that arc treated characters like Turtle Tail and Bumble, basically blaming them for being abused

Female characters dying to give the male characters someone to grieve over is awful, but for another reason than just that. Because even in that scenario the she-cat’s life is still reduced down to her relationship to her love interest and nothing more. Remember how heartbroken Crowpaw was when Feathertail died? How she spend her dying breaths telling him she would always be with him. Why was her death written to impact Crowfeather more than Stormfur? Why wasn’t Stormfur written to be devastated? Why didn’t Feathertail talk to him, her brother whom she grew up with? Feathertail and Crowpaw barley knew each other when Feathertail died, so why did he have to be the main focus? Simple, because it set up Crowfeather’s character and gave him someone to grieve over, and also made it so none of Feathertail’s other relationships in her life matter other than the romantic one.
Characters can love each other without being mates because there are other types of love who don’t the Erin’s get this?

The text itself is extremely sexist/misogynist. You can not deny that, regardless of intent or not. It is so extremely frustrating, and I’m glad someone finally agrees with me on this.

"all she cats should have a mate and focus on their family" omg this.. I recently reread the first series and the part where fireheart questioned if Cinderpelt was sure about becoming a medicine cat when she was actually excited about it because "what if she wants to have kits" 😭 there's no way they'd write that about a male medicine cat (could be wrong cause I haven't read beyond that series but it stuck with me cause it really echoes how human women are talked to sometimes)

After reading River, Sunbeam hits so hard into the female archetype of expecting to have mate and kits that i physically cringe in her chapters, yet Frostpaw is the complete opposite being a medicine cat apprentice with the entire clan at her paws. I swear they show they can write good characters and they finally have one good female but I know they'll screw it up somehow.

This is EXTREMELY small in the grand scheme of things but I'll never forgive the books for constantly referring to Dappletail as a 'once pretty' she-cat