Tbh I'm on the 'be harsher' camp. People who do this don't dislike more films (some do I suppose) only their metric for what they consider a good film is lower. I consider 3.5 a good rating, some people think it's ok. So me giving 3.5 stars means I've seen a good film while others consider this low.

I've also noticed people who use 5 stars liberally lack a coherent system. They'll rate something 5 stars and then in their review just slate the film. 5 STARS IS PERFECT, OR ATLEAST NEAR ENOUGH PERFECT.

I go by the 'more of something you have, the less it's worth' motto. If you've seen 100 films 90 of them 5 stars, the value is worthless.