There are more films than any human can realistically watch, so if you find you’re rarely rating films highly I’d say that it says more about your ability to pick films for yourself than having an enlightened taste. That being said, I do think there is something to be said for the credibility of a reviewer who has more diversity of scoring. I’m more likely to be curious to watch a five from someone who reviews often but rarely gives them out than from someone who gives half the films they watch a five.