I don't think 2D animation would be a strict improvement.
To start with, the only reason the PV looks as good as it does is because they had three minutes tops to impress investors on what ZagToon had to offer. If this was a 20 minute episode out of 26 others, the animation quality would've been stretched thin with how tight deadlines and budgets are.
I mean, the Anime community is getting a harsh reminder of this with One Punch Man...
Same with Miraculous Tokyo. Odds are the Stellar Force's main TV show will be a lot more constrained in their presentation over multiple episodes. That's just how it goes with animation production even when the production crew isn't being crunched to death for slave wages.
Frankly, I think Season Six's animation style is the best by far. The design changes are questionable but it avoids when Season 4 and 5 felt too… on-model if that makes sense. Less stiff and more moving even when they're standing still.
Plus, the writing would be the same so we'd still be having the same discourse but coated in a different look.
