What I find truly frustrating with this review system is that we all have the same rating, good or bad stories.
My 4.8 is genuine (I don't say it is worth 4.8 though. 4.8 should be a near perfect masterpiece) : except for 1 star review at chap0 reading status, I've deleted every 5 stars spam reviews. I only keep one from each reader since we can't check our readers' profile anymore either.
It is frustrating because with this review system, my rating becomes worthlesss and even worse people will accuse me to manipulate my ratings. A too good rating basically becomes your worst enemy to bring new readers when it should have been the most trustworthy indicator to decide if a story is worth reading or not.
The problem is that even if you can prevent authors to delete bad reviews, there's still ways to keep a good rating with bots and alt accounts.
I have a long list of novels/authors that I could mention here that keep every 5 stars spam reviews and/or delete bad reviews(even legit ones). I could even give you a few that I suspect to use bots/alt accounts to drown their review section with spam 5 star reviews.
Now even if Webnovel doesn't have enough staff to create a real moderation team, there's one thing to implement that would fix 80% of the problem: Readers should only be able to review a story once. If at some point their opinion of the novel changed, they can just edit their former review.
Believe me... That's the first step.