I can confirm that it’s fixed on Netflix, thanks! Unfortunately it’s still broken for me on Youtube. Interestingly, I have subtitles set to Chinese (Simplified) and if I hover over English words the dictionary pops up (with only “…” in it) but when hovering over Chinese words nothing happens.
You can’t see my mouse but in the first image it is over “vlog” and in the second image it is over “大家”.
Testing on this video: 【VLOG in Chinese】ROOM TOUR 2021 - YouTube