I don't know how to define excessive in this case, but it made the website much more tolerable for me, and I'm grateful for being able to do it.

The thumbnails are very distracting, and I found it hard to pay attention to the video playing on screen.

I don't miss the thumbnails at all, not one bit.

Interesting idea, I will try that. I have disabled almost everything I could on YT (feeds, comments, video overlays, recommendations, history), but occasionally still encounter the horrible twisted-face-pointing-finger thumbnails.