The "just works" nature is why Zoom is popular. No one wants to have every meeting start with "Is Larry here? Oh, I think he's trying to dial in. I'm going to cancel this meeting and send out a new ID so he can dial in. Everyone watch for that so you can reconnect"
You could even include the option to get approval - pop up says "Mx. Caller ID is calling from 555.555.5555. Approve?" Obviously there's no way to get in through random dialing. And if you get a pile of requests, provide a way to filter incoming numbers and disable the calling ID as soon as everyone is in.
That's even assuming that anti-DOS protection on the phone line is impossible.
