今際の国のアリス S1

I think it's worth watching alone for the story, characters, production quality, entertainment, etc.

Language-wise, I do agree that it has a lot of downtime. But it's an action/thriller TV show, not a book, so that really shouldn't bother you. It was actually kinda hard to understand Alice at times, the actor really loves to slur his words, which is a good thing learning-wise, because people don't speak with perfect enunciation, you know? Otherwise it's quite standard Japanese.

I don't agree with the rating as it is (Lv 30)

There's barely any dialogue, and the dialogue that is there is super easy to understand. Why people think it's difficult (at least season 1) is beyond me. The show is entertaining don't get me wrong, but for difficulty this is easily a level 25 show with like 2 or 3 lookups if you don't know kanji for rules like time limit, etc.