I mean... I don't really have a response to this. This is security modeling 101. To different threat models, this is a varying degree of a threat - anywhere from "not a threat" to "unacceptable threat".
You cannot universally answer the question "how much of a threat are chrome extensions".
I understand that this is a pet peeve of yours. But what exactly stops you from learning what kind of data chrome extensions have access to (they can see everything on any page you visit and send it to perpetrators) and assuming the worst?
You cannot universally answer the question "how much of a threat are chrome extensions".