My list scores are derived entirely from how much I enjoyed the anime. How universally popular or how accessible an anime is to people has no effect on the score I give, because those factors do not influence my enjoyment of an anime. In other words, my scoring scale is completely subjective to me.
If I give an anime a 10, that does not mean that I consider it to be absolutely perfect. It means that what flaws the anime has are so negligible or unimportant when compared with how much I enjoyed it that the flaws simply don't matter to me.
An anime doesn't have to be deep to be good. Sometimes it helps, but I think watching anime should be fun, and that's why I rate the way I do.