As someone who is mostly remote, I never had too much of a problem with hybrid meetings. People in a conference room are pretty respectful that there are people on the phone in my experience. That said, the current situation where everyone is dialing in individually is something of a meeting upgrade overall. People have also gotten better at collaboratively edited agendas etc. not that they were bad to start with.
Seems pretty extreme to require everyone to dial-in even if they are present in the office.
Btw, I'm also a big fan of remote working, but no matter how good your communication skills are, you're left behind on the longer term within an hybrid team. You just can't build all these relationships with smalltalk etc. that's another problem
Even with over 500 employees, the lack of a career ladder as such meant there's little to gain by being the loudest in the room or trying to work the room. Perhaps that's also an ingredient - it might be easier to minimise others' egos when you're also in the room?
That's also one reason why many people on autistic spectrum prefer video conferences over physical meeting - responses have to be given more explicit.