If Google follows the model with Chrome that they did Android, UXSS permissions will eventually be phased out over time and replaced with better, more secure, opt-in, purpose-built APIs in Chrome. (Assuming they can do that without sacrificing _too_ much functionality.)
EULAs, Terms of Service, Mobile Apps, Cookie Consents have boy-who-cried-wolf'ed everyone except the most paranoid and tech-savvy to the point that they are mostly ignored.
Yes, many non-technical users do not pay attention to permissions. But permissions are extremely helpful to people who do use them -- and the number of people who do use them is larger than the number of people who audit source code or set up VMs.
Educating normal users to pay attention to permissions is a problem. It is a separate problem than, "do they even have tools in the first place if they want to use them." The problem I want solved is how I verify that an extension is safe. Granular extension permissions solves that problem for people like me.
After that problem is solved, then I can worry about educating my friends and family.
No idea if that's included in Google's plans for Manifest v3, but I agree with you that it _should_ be done that way if at all possible.
That and the ease that you can revoke permissions. No going into a separate settings window, just click next to the URL bar and everything shows up.