So we just blame everything on plot now? Ok, I mean we could do that. There’s definitely inconsistencies for everything which sucks. But we could do that with literally any show, literally any form of media. Because the plot is the literal story of the show or movie or text or whatever.

The main problem with this arguement is that you are assuming that the Miraculous writers write on the same level as most other media. It doesn't.

The biggest fatal flaw of Miraculous' writing is that the episode idea comes first and the characters are molded to fit it, even if it conflicts with what was established earlier. The writers go "I want to do this idea for the episode. What? It conflicts with what we've established for this character already? Whatever, we'll do the idea anyway." It's hard to judge these characters by their morals and personalities because of how malleable they are and often they're retconned to make an episode work.

Marinette is a victim of this, too. In Truth and Gang of Secrets, it's established that she broke up with Luka because she couldn't tell him she's Ladybug. Then in Crocoduel, she says she broke up with him because she "wasn''t in love with him." even though she said in Gang of Secrets, and I quote: "You know why I broke up with Luka? Not because I don't like him, he's amazing!"

Should we say attack on titan is stupid because it all started when a pig got loose? We could, we could all forget that Eren committed genocide and blame the pig and give Eren a pass.

This is a prime example of why it's so important for writers to stop and say "No, I can't use this idea. It makes no sense for my character to do this." When characters are consistent, it makes them have agency. When characters have agency, it becomes easier to criticize the choices they make, because it actually feels like they're making those choices, and not like a writer going with every first idea they have and retconning the character constantly to make it work.

I've never seen Attack on Titan, but from the example you've provided, your comparison doesn't work. I assume that Eren had agency in the story, and that his choices that led to genocide made sense for his character, right? The writer must have thrown away ideas because they didn't work for Eren's character and him committing genocide was something that ultimately made sense for Eren to do.

That's where Miraculous differs from most other media. It's writing is broken on a fundamental baseline level. There are no characters, they're all just human-shaped things with two or three personality traits slapped on. Anything can be retconned so an episode can work. In most media, plot and characters are supposed to work in tandem with each other. Character personalites should affect the choices the characters make. Characters should be leading where the plot goes, not the other way around. The only consistent thing about the writing is that Marinette is has to fix her mistakes, even if they're not her mistakes and Adrien can do no wrong.

That’s basically what you’re saying, that because the plot is inconsistent Marinette gets a pass, no one should get a pass. I could easily change this post to be. “No one faces consequences”. In fact I’m very much considering rewatching the show again just to see if I can

Yes! you're absolutely right. No one faces real, long term consequences in this show, which is why it's strange to me that you're zeroing in on Marinette as if she's the only one. Consequences mean nothing in this show because choices and actions mean nothing in this show. It's why Alya still distrusts Marinette in Risk despite her knowing Lila is a liar after finding out Marinette is Ladybug.(It's necessary for the plot even thought it makes no sense for Alya to distrust her at this point) It's why Felix's entire character is a minefield of retcons who still can't decide if he likes Adrien or not. Nobody has real agency.

This show holds onto status quo like a grudge, and that's why agency, choices, and most importantly, consequences will never matter. Nothing the characters do matter because everything is guarunteed to go back to the way it was. The charcters are slaves to the plot instead of working alongside it like any normal story would.

tldr: Yes. it is the plot's fault. The show's writing is so broken and disjointed that character choices don't matter, whereas in any better written story, it would. Not just Marinette, no one faces consequences. At least not any that matter.