IMDb's TV ratings are a joke.
There are so many problems with it.
First, there are way too many mediocre shows that are an 8.0 or higher. It might be a result of my second point.
Second, you can vote for a new show that is only a few episodes in. For example: when Westworld was only 4 episodes in it was an 8.9. Fans of the series didn't love the second season and now going into its third season it's now an 8.8. Too many people gave it high scores when it first came out that it's going to take a lot more ratings to bring the score down.
Third, how can you even rate a show? Should you give a score for every episode then average it out by the end of the season? Do you give a score at the end of every season and not the individual episodes? Do you wait until the end of the series to give it a score even though if you rated every episode individually, it wouldn't average out to the final score you gave it?
I think that's why the TV scores are all over the place and that's why you see so many shows with high scores.