> What exactly is your gripe with MV3?

Running an adblocker is the defining feature of the extensions API. ublock origin has 5x as many users as the second-most-popular extension [1]

Supporting ublock isn't just a nice-to-have add-on feature for an extension API, it's literally the only thing most users care about.

[1] https://addons.mozilla.org/en-GB/firefox/search/?promoted=re...