Let me rephrase then: cookie prompt blocking capabilities are not tied to the Manifest version

never said otherwise.

But we're discussing the ad-blocking features, because these are the ones affected by Mv3, no?

no. that is not the only feature affected by Mv3. it is just the most noticeable feature affected.

Define "not so effective". What's "effectiveness" in this case?

ublock has many tools to defuse tracking mechanisms. it can fake browser mechanisms, it can stop scripts when they do a certain thing, it can replace entire javascript functions. it can modify outgoing network requests and incoming responses to them in many ways, which privacy badger does not implement. I don't want to include multiple pages of text here, so please go through the wiki pages of the uBlock Origin github repository, because it details all the capabilities and technical details.

but as even the main uBlock Origin maintainer says, the addon wouldn't be worth anything without all the community sourced filter lists with quick fixes and specific blocking instructions for lots of websites. compared to that, privacy badger does not use filterlists. it can only do things that can apply to any website without breaking it, and that limits the options a lot.

OK, but again: what's the difference for the end-user? Does it impact resources utilisation? Website loading times? Reactivity? I don't see a difference in how my uBO browser behaves vs how my Ghostery browser behaves, so what am I losing because of the Mv3 switch?

I'm starting to think that you might be not arguing in good faith. but it is certain that we are going in circles and I'm wasting my time. you should look up the wast documentation of uBlock Origin and you will get all the answers, if you are genuinely interested. there are probably even technical comparisons between uBO and lite from the maintaners