In the limited style of anime, making characters look their age is just impossible. But, then again, I've seen some great looking elderly characters. Pinako Rockbell looks her age, and I guess suppose Madam Ping looks old enough. But, for the most part, I'd say a lot of Genshin characters look young. For some, you can't really blame them. Ganyu is partially an adeptus, Zhongi is an Adeptus(?) too, Xiao is a Yaksha, and Dainsleif is cursed with immortality.
Then there's characters who look like children when they're adults. But, I don't think Genshin has this problem. At least, I don't think so, anyway.
And, I can agree with it being difficult to portray different stages of aging in art form. I'm not an artist, if you've seen my various drawings, I suppose you'd know that. But, I can't really draw a character in their thirties look to be in their thirties.
Haha, imagine... makes me want to write a shitpost fic of that for some reason. But, I don't have time. Sunday is tomorrow. Got a fun corrosive acid rain chapter to write.