I too have experienced this existential dread, and sometimes still do.
Your post triggered a multitude of responses from different people experiencing the same, each with their own set of beliefs and coping mechanisms.
I found it fascinating - thank you.
It always surprises me that we are in a minority - most people go through life without experiencing this, or wondering about this. When trying to discuss this with one of them, they are usually baffled, and truly cannot understand you. It is almost as if we're speaking different languages.
As a side note - I am wondering if there is something in common in all those who experience this dread.
I think there are a few other issues with meetings except for just fast thinking.
Some things I tend to better understand when written down. It also allows you to search for additional context which is harder to get in a meeting (it could seem as derailing the meeting).
Another thing is just timing and energy levels. You're not your 100% self in a meeting, but you can choose when to review something offline, and answer accordingly.
OTOH, I admit that meetings do spark some ideas from a back-and-forth quick exchange, which otherwise might've been missed, or would've taken long to get to.