Let me say this again, Teams works perfectly on my machine, it's largely indistinguishable performance wise compared to Slack on the same machine, if anything it runs a bit better.
I'm not going to try claim Teams isn't in fact terrible for other people, my point was that as I suffer no problems with it, it makes me wonder what's different on my machine compared to these other people's, and as I don't have any security software except Windows Defender, I speculate it's maybe their corporate managed security software is a factor.