I think this is more targeted at new graduate students.

I remember when I first started my PhD, literally all of the talks were completely over my head, and I did not understand enough to engage as you describe here :)

Gathering three key takeaways would already require a good deal of effort :) and, I appreciate that the author of this post absolves you of having to have the speaker’s message as a key takeaway, since as a beginner grad student that is frequently beyond reach.