Tacky

I sometimes visit the r/FanFiction subreddit. Today I brought up my practice of reviewing fanfic there, and another user said that, in their opinion, writing unsolicited negative reviews is "tacky" because fic writers are not professional authors.

What do you all think of this? I suppose that people who follow the journal of a person who writes such reviews might be a biased sample, but I'm still curious.

Personally, I see it as one of the things engaged fans do. I know there is plenty of precedent for it in fandom, and the reviews of the past, as quoted on Fanlore, are often much less gentle than I try to be.