I'd think these shouldn't be any need for character descriptions in appearance/personality when we're talking about Reimu, Marisa, Yukari, or any of the very big characters imo--lesser-known characters, possibly the PC-98s or minor print work/cd characters that people don't know about, should probably have it though? Otherwise, save the description for your own headcanons on the character.
But yeah, if you want to roleplay, like I said, Reimu or Marisa or Cirno or smth, I don't think you'd need a description since everyone knows what the characters are like, unless you're using an AU of the character and such.
Basically yeah, I agree, to a part.