Why does MS Teams struggle with 200 users?

At work we used Microsoft 365 for Business. As a consequence, we also use Microsoft Teams for Business (I think that's the correct name). I work as a software engineer. The IT group is about 200 people, which includes all the developers, IT Admins, DBAs, etc. For a couple years we've been using MS Teams for our group's meetings. We also use MS Teams for agency wide meetings, which normally brings in 500+ people. 

However, for a while now (I don't know how long, because the IT group doesn't share that information) when we've had meetings involving all of IT, sometimes people loose connection and get dropped. They reconnect to rejoin the meeting, but it has become a problem. So much so that the agency is considering dropping MS Teams entirely, in favor of Zoom.

Personally, I like MS Teams more than Zoom, but clearly this issue must be resolved. I had thought that Microsoft had made MS Teams capable handling thousands of simultaneous users in a meeting. So, what gives? Why is MS Teams behaving so poorly?