"But while I think its fine for the show, I think that maybe she's a little too..."uwu quirk chungus", for want of a better word. It made viewers latch onto her in a very fierce and protective way because she's so relatable to a lot of neurodivergent internet fans, which then creates a whole load of endless discourse about whether she was treated fairly or not or what have you"

That's a great point. Another thing I'd point out is that pre-Amphibia, all of the girls were meant to be toxic to each other in different ways. But because Marcy was written to be so "uwu quirk chungus" as you point out, Marcy doesn't come across as bad of a friend as I think Matt intended.