I have the same problem and I'm f*$^#& mad. Unfortunately, that's not a bug. At least that's what administrators think. Damn, I really want to have the old bar!
However, there is hope! A developer said that they're working on it! https://www.chess.com/forum/view/site-feedback/i-do-not-like-the-new-smaller-analysis-bar-61557381?page=3#comment-61643703
My evaluation bar has no numbers on it, and is much thinner. Driving me insane - what can i do?