"This looks like mobile game BS." - By far the most common, despite there being no single 'mobile game' monolith using 1 art style and a general inability to name any mobile games. At worst they mean it looks like a Supercell game which isn't even a bad thing, their art style is great.
"WayForward don't know what people liked about AW, they're already ruining it." - AW was only popular for pixel art that only took place in battle animations apparently.
"This reeks of corporate meddling, greedy management types cheaping out to make as much money as possible." - a big extrapolation from a change in art style.
"Advance Wars was never this childish and it's alienating adult fans/they won't let me feel like a war commander now." - aka gaming meets toxic machismo.
"[Some weird weeb **** about western animation all looking the same and being crap compared to anime stylings]" - I am a weeb but these attitudes are ridiculous.
Yeah, I've seen a LOT of bad takes, and that's not even including the amount of people who take a more mild stance on the "Advance Wars shouldn't lean this hard on the childish side" by completely misrepresenting the originals and thinking they were all more similar to DS in tone. They're not toxic but I just don't know if they really remember the first 2 games.
But yeah, the game will survive this because there's generally some good inertia behind it as
Ura
and
meleebrawler
pointed out, the series has been next to F-Zero in notably longing fans at Directs and we don't even have a Smash character (yet) to keep it relevant.
Despite the tweet I don't think there's going to be much changing from the preview, even in the art unfortunately as I do think the models could be improved (but not in need of an overhaul or anything just some tweaks). That said I do think the price point is a valid criticism if we have no promise of rebalancing or future content, but I will be buying it because value is subjective and it's worth it to me.