Sobble one was definitely the biggest one, and extension Grookey too. Either one of them of them would have been better utilized under Ash's ownership instead of Goh's. Ash could have raised Sobble on screen to become more confident instead of it just being Goh's shoulder mon and later lay around in cave until it gets its unearned evolution, as for Grookey, Ash could have channeled all of its destructive energy into battling, plus it was clearly interested in battling.
Side notes: When Lana Caught Eevee/Sandy(?), I actually didn't really mind all that much. I didn't like the haircut though, made him look like an
acorn.
As for Chloe, here's a fun idea, what if during JN she caught Pokemon based on the types of the Eeveelutions, with G-Ponyta representing the Fairy and Psychic, Yamper being Electric, Lotad being water and grass, and so on with the other eeveelution types, even using that water stone she was given cause you all know that was never gonna be used on Eevee.