I really enjoyed "The Calculating Stars". As did apparently many other people.
It's totally normal to dislike some winners, I certainly don't like them all. But that doesn't mean quality is down - it's a matter of taste, after all.
Books do exist that are objectively bad, but consider that maybe this time - and other times - this is just a matter of taste. (And it's entirely possible that the folks who pick out Hugo winners don't match yours, and that's fine.)
But a book like "The Calculating Stars" is just so bad, I'll never trust the Hugo award again.