I've never liked Slack, but it's UX perfection in comparison. I'm so sorry you have to tolerate MS Teams. Have you thought of quitting? Joking aside, it says a lot about a company when they use MS Teams.
Slack is ok. Its latest redesign added bugs and made the interface quite annoying. It could be much better with a few trivial tweaks, but it's not terrible either.
Also, I don't know if teams handles it any better, but slack has absolutely no offline capabilities / cache on the desktop. And electron sucks for electron reasons.