It's all about personal preference. From my perspective, I view reading as a conversation between author and reader, so I, as a reader, ought to at least make a good-faith effort to understand what the author is trying to accomplish with their book. Bad reviews that focus on taste but clearly miss the point irk me (for example, when someone complains that a YA book are too simple when YA books are targeted to a younger audience, or mismatched genre expectations like a horror book being too scary—I've seen all kinds of iterations of these types of reviews).

A book can be a good book, but not for you.

A book can be a good book, but not for you at that particular time in your life.

That's not to say that readers aren't entitled to their opinions, but giving low ratings to books for not being what they weren't meant to be in the first place isn't fair to either the book or other readers who are actually looking for that type of book.

I'm also of the mind that if you give too many five-stars, when you come across books you really, REALLY love, you have no higher rating to give them (which is when you start seeing the "six-star books"). So I can see the argument for reserving five stars for truly exceptional books that leave a lasting impression on you.

All that to say, this is why I can't stand using stars anymore! 😂 Of course, you could get very granular and use .5, .25, etc., but why? (again, that's personal preference for me. If it's helpful for you, by all means, use it).