My organization has the same experience as you when using MS Teams.
It is impossible to share a video during the call and even PowerPoint slides lag every now and then.
Using the same hardware, we don't have this problem using Zoom, WebEx, or Goto Meeting.
My office laptop has these specs:
Intel i5-8350 @ 1.70 GHz
16.0 RAM
Windows 10 Enterprise and Office 365 Enterprise Subscription
I even have this problem when I'm on my gaming laptop with a 1GB internet connection.
It almost as if something is throttling the speed/connection. I've tried clearing caches / running only MS teams and PowerPoint / switched between LAN and WIFI, reinstalling the App, and nothing works.