I don't care that much for following Pokemon to think that it's absolutely needed for the game to be good, however the fact that its nowhere to be seen in S&S should serve as an immediate redflag that they're treating it as another lazy cashgrab.
They have had all the animations laying around since SM and if they had to make new ones for the new Pokemon then Creatures inc. would've done the job, and Let's Go already dealt with sizes by making the mons automatically go inside the ball when the space gets too thight so there's literally no excuse for them.