Mind if I ask what OS you're on? On macos I use teams a lot and it is very fast even when resources are tight yet you're not the first person I heard say it is slow.
Video playback and taking calls on a second, larger (40” 4k) display, have improved slightly but are still bad enough that I’d rather move the app to the laptop’s display (32gb mbp mid-2020)
I do think it’s a second-rate app compared to most of Microsoft’s usual offerings - OneNote being a notable exception. Other than the video item above, I’ve found overall performance to be adequate and not remarkable one way or the other.