Who tells everyone to use that scale though? You're presented with a row of stars. Expecting people to read winds up being a big ask.

Also, those categories are subjective as well. What's the difference between "bad" and "really bad"?

Mutual graded rating systems suck. That's all there is to it. Because no matter what, it turns into currency. "Yes/No" and then base a rating on that. Rotten Tomatoes had it right from the start.