It can feel like a waste of time.
But… you should allow people to do this.
Extroverts do their best thinking while they talk.
And many extroverts get their energy from exploring new ideas.
So please don’t cut them off or stop them in their tracks. It’ll drain the energy from them.
Instead, show enthusiasm. Explore the idea for a couple of minutes.
And then, gently suggest another meeting to discuss the idea because this meeting is about X activity that needs doing.
Often they won’t even want the other meeting. They just want the space to think through their ideas.
You’ll get your meeting back on track.
And the extrovert will be on your side because you validated their need to explore new ideas.