Why I don’t use the star rating

If you’ve been reading my blog, you know I don’t write reviews. I write about a subject—my thoughts, observations, reactions, and if lucky, sometimes I point out something that most people haven’t noticed or haven’t talked about. Like the silences in The Portrait of a Lady, for example. Or the dog motif in Lolita. Or the different kinds of smiles in War and Peace. Or the tortoises in Melville’s “The Encantadas”. And so on. 
I definitely don’t write book summary. There are lots of book bloggers out there who spend almost an entire post summarising a book and add about 3 lines of their thoughts, which I don’t understand. I don’t do that—after all, what’s the point of another blogger/amateur reader introducing the plot of something like Anna Karenina or Moby Dick or Strange Case of Dr Jekyll and Mr Hyde? Everyone knows the basic plot. 
I don’t use the star rating either. Just now, I came across a blog, in which the author rates Lolita as 4 out of 5 stars, but gives The Great Gatsby 5 stars, Never Let Me Go 5 stars, Villette 5 stars, etc. What? 
I mean, the whole star rating thing just confuses me. If I go by my aesthetics, Emma would get 5 stars because it is perfect and skilfully written, with a masterful use of the free indirect speech, and Middlemarch would get 4 stars because it is baggy and the moralistic author is intrusive, but at the same time, Middlemarch is a much more ambitious and expansive work, and could be said to be greater.
Even if I mean it so Middlemarch is not compared to Emma, because they are incomparable, how do I tell people that I mean Middlemarch gets 4 stars when placed next to other works of large scope such as Anna Karenina, War and Peace, and Moby Dick, all of which I give 5 stars? If I give all of these 5 stars, how do I give Madame Bovary 5 stars, which it well deserves, but at the same time I argue that in many ways, scope as well as depth, I rank Anna Karenina much above Madame Bovary? I can’t give Madame Bovary 4 stars, because if I do, how do I rate the other works of similar small scopes (focusing on a handful of characters), such as works by Jane Austen or the Brontes? 
Or if I place Jane Austen’s novels next to each other, suppose I give 5 stars to Emma and Mansfield Park, what do I give Pride and Prejudice? It doesn’t have any obvious deficiency to get a 4, and do I give Sense and Sensibility 4 and Northanger Abbey 3? Or what? Sense and Sensibility and Northanger Abbey are both very good, they are just thin and don’t have the depth of her later works. 
All of it is confusing. 
Then comes the question of importance. Crime and Punishment is a deeply flawed book, and Frankenstein doesn’t have very good prose or great writing either, but they stand the test of time because of their philosophy and influence. I don’t want to give them 5 stars because of the imperfections (and conflicts with my aesthetics), but wouldn’t it be insulting (and not very humble on my part) to give them 4 or 3? Rating feels almost like giving a mark—who am I to give such literary works a mark? 
Or if we see the rating as an evaluation of what a book is, against what it could be, for example, Emma deserves 5 stars because Jane Austen uses the free indirect speech to depict Emma’s character, describe events through her perspective, and at the same time fool the readers, i.e. she succeeds in what she apparently sets out to do, then how do we know such a thing about books in general? Or are we just guessing? Crime and Punishment is imperfect, but what could it be? I have no idea.
Even if we judge books by such standards and it somehow works, I don’t like the idea that works of remarkable scope, depth, and importance like Anna Karenina and Moby Dick get 5 stars, and a well-written but much less ambitious work like Emma also has 5 stars. There’s something wrong there. 
Maybe somebody will explain to me this whole rating business.