I find the character customization in terms of the face to be good, though it could do with more makeup options on the eyes. I find their hairstyle options to be a bit lacking and, like in Pokémon Legends: Arceus, am disappointed in the lack of longer hairstyles for the girls. There's only really one and if you don't like it then you're out of luck. I like the color variety for hair at least.
As it pertains to clothing, the inability to change out of the 4 uniform options and the exclusion of skirt options is a definite downgrade. I got used to it over time and begrudgingly accept it; I still wish we had more options like the previous games offer, but I've managed to make a few outfits that I am happy with. There arises a problem, for me, in that there are a bunch of color options for things like gloves, glasses, hats, socks, tights, etc. that don't go with anything. Like, why am I going to pick green or yellow for any of those things in either Scarlet or Violet? They don't go with the uniform colors very well. Some of the color options also obviously compliment one game more than the other, like the red and blue complimenting Scarlet because of Koraidon, and the purples and pinks complimenting Violet because of Miraidon. It seems like there was a lack of quality control and oversight when it came to making sure that things go together well, which is unsurprising considering the rushed, crunch development for these games.
I can appreciate the concept of the uniforms, I see what they were going for, but it's a bit restricting. I hope the next games are a return to form from the previous games.