I've come to realize that Teams should only be used in large companies who can afford dedicated staff to manage it. But it was certainly sold to us as being easy to use and suitable for a small company.
I mentioned that because security software blocking things locally or at the network level is such a common source of friction. I don’t think Teams is perfect by any means but the core functionality has been quite stable in personal use, both of my wife’s schools, and my professional use so I wouldn’t conclude that it’s hopeless and always like that.
I also had to add a new user yesterday, so I went to admin.microsoft.com in Edge. 403 error. Tried Chrome and Firefox. Same. Went back to Edge and suddenly it loaded. The like an idiot I refreshed, 403 error again. Another 5 or six refreshes and it finally loaded again and I was able to add the new user. There's never any real error messages that would help me debug anything, it's just endless frustration and slowness.