"Decline."

Working in IT, I have learned that a lot of meetings are by people who gain "respect and notoriety" by having large meetings. It doesn't matter who shows up, it's the number, that makes them seem popular. "Get the engineers in here, this is serious business!" You begin to learn which PMs do this, and can respond (or not) accordingly. If they ping you "where are you?" you can say, "I am in an [client] audit call. I cannot leave this call while the audit is taking place." Or whatever your industry equivalent is. YMMV, some toxic environments I have been in, this was not possible.

I remember one PM was frozen in indecision. I had to tell him, "I can fix the problem, or having a meeting about it. Pick one."

"Well, both--"

"No. I can fix the problem, or having a meeting about it. Pick one or the other."

"I need you in this meeting!"

"When we explain to the customer that the fix was delayed by an hour, I can use YOUR name, as having a meeting about it instead of fixing it, correct?"

"The meeting is to be about fixing it!"

"No. I can fix the problem, or having a meeting about it. Pick one or the other."

"... we can have the meeting in your office, then."

Eventually, my boss shooed him away.

Isn't that normal for everyone?

Actually the right side graph needs a correction from my point of view. The decline in productivity doesn't happen sharply when the meeting starts. For me the decline starts between 15 to 30 minutes before the meeting slowly, as I can hardly concentrate concerned that I might miss the start. If I'm ever in hyper concentration mode, most likely I'll miss the start of the meeting.

As an engineer I approve this message

This is the best explanation for why this happens that I've ever read.

https://www.paulgraham.com/makersschedule.html

I heard about it on Freakonomics, and having been both a creative and a manager it really hits home.

the worst is the unexpected meeting a couple hours later because then you also get the pre meeting productivity drop as well (from the mental anguish of having to go to that meeting an hour later)

I have been having to attend these asinine meetings for an hour a day for the last month when they were twice a week for far less time. But since we have an emergency situation the whole plan is discussed with everyone so many times. I know it's a pain, but I feel it takes me away from what I should be working on. I hate it.