I mostly rate anime mainly how much I liked watching the show (enjoyment) . How much the anime intrigued me. That includes art,characters,story etc. A score for anime can change.
10. I must really love this show and would re-watch it (probably my all time fav)
9. Simply great but had some small flaw that stopped me giving it a 10
8.Above good but might have some minor things I didnt like about it but still very enjoyable
7.A good show to watch but nothing really Special ( could have been better)
6. Not bad but not that good. I might have struggled finishing it.
5. The Anime was pretty disappointing. It Has high chance of being dropped unless for some reason I decided to watch it till the last episode.
I dont give below a 5 because I havent watched the worst anime yet lol.