What happened instead were impromptu "ghost" meetings and a ton of stuff done sloppily over chat instead, where I think the hope was that people would try to become "more efficient" with their meeting time.
Required meeting attendees should consist of the Rs... and only the Rs. As and Cs can be optional, but meetings can conclude without them.
Everyone not in the meeting can be updated out of band.
"What action is this person taking in this meeting?" should be a brutally honest question. If the answer is only "listening", then it's a waste of their time.
And also, related point: what is the termination condition of this meeting? And has that been decided and communicated beforehand? I.e. What outcome are we seeking, that when done everyone agrees the meeting is over?
I can't stand agenda-less, "we're meeting to move something forward in some undefined way" meetings.
Is the purpose of the meeting to inform, decide, workshop, or persuade?
If it's to inform, it should be an email, but some people do not read them, so you need to sometimes read the email to them in a meeting.
If it's to decide, do you have the people that will decide called out in the agenda? Do they have the necessary information or have they done the necessary work to make a decision in the meeting?
If it's a workshop, do you have the invitees pared-down to those that will be actively participating? Is there work they need to complete before the meeting, so they can be active participants?
If it's to persuade, these should be in smaller formats. Preferably 1-1 to start, so objections and resistance are raised in low(er) stakes meetings.
Meetings should end with a summary of decisions, next steps, or some other call to action. Preferably these are recorded somewhere and distributed to the rest of the attendees or a wider audience if needed.