Yeah however for mass adoption this is a terrible idea, there is already the extra step to choose an instance versus a regular social media that is just one link and one button.
I know for people like you and I choosing an instance isn’t that big of a deal, nor is an extra extension (though i try to use as few as possible) but for a regular user it might cause issues.
Yeah an extension is no more trustworthy than the source providing it, network level adblock which you can monitor completely is probably the correct route