Earlier quoted context omitted.
I switched to fish a very long time ago (2009 maybe?) because it started up so much faster than zsh w/ all the plugins that it took to get the fancy features fish had out of the box. Since then, fish has only become a lot faster as we have focused on performance and optimizations considerably.
I tried zsh after fish and my impression was somewhat like this: Okay, so I got to do a lot of customizing to get this to work nearly as well as fish does out of the box - can't be bothered!
When I was in school and working on my own stuff I liked using fringe shells like xonsh and fish, but working in teams I feel like I need a pretty significant productivity increase to justify using a different tool than everybody else.