Quoting me from Reddit:
To be honest, if you ask me, a 5 stars voting system instead of 0 to 10 is too much limited, i mean: 4 means that it's a game that might be worth from 6/10 to 8/10... way too vague.
Considered that 4 stars can describe both a good game and a meh one, no wonder it can be perceived as bad.
Also, rather than a not perfect game, 4 sounds like a... not a 5 (meh), basically from my perspective of gamedev i perceive it like the vote that crushes your streak of 5 stars ratings.
So i don't like to give a 4... i'd rather give a 5 if i think it would be more likely a solid 4, in that way it won't be perceived as negative by anyone.
This is Itch, not Steam: more than average is not a masterpiece, let alone a budget game! You cannot use conventional criteria of more popular gaming for indies who probably cannot even afford 100 bucks for the Steam page (and some of them yet make a good game!). The best ones will be distinguished by getting tons of more votes, review, comments, visibility... and maybe even some concrete earnings. Don't you think that's already more than enough, as difference? Just let not-perfect itch games get their 5 stars, no one will be penalized from doing that.
If i don't think it can possibly get a 5 stars by any way, then i just don't vote: it's so hard to gain some genuine vote, when starting from scratch: it feels almost cruel to even give a negative one and destroy the game.
Blatant scams or tremendous game you probably don't even try the game so you don't vote as well, even giving minimum vote to scammers sounds as too much exposure for scammers, so it's just better to not feed them.
So in the end rating on itch i perceive it as a Yes (5) or No (don't vote), and probably i'm not the only one who perceive it this way