I don't need any MV2 extension, so I don't really care.

So, you're fine with the ads and tracking.

Brave has built in ad / tracking blocking without using MV2. If MV2 vanished in Brave you could still have blocking without using uBlock Origin

Almost nobody cares about anything other than ad blocking and to top it off the reply to the comment you linked is even mentioning that they were only talking about ad block...

You may be right, but I have no trust in Brave. Not just due to their shady decisions in the past but also because they would have to fight a huge ad industry on a tiny budget with their built-in ad blocker. At least if it's an add-on, the community would be able to help easier.

The discontinued support of MV2 means that all ads will eventually adapt and your anti-ad measures stop working.

I think you don't understand the difference between an extension (for which manifest version matters) and an intrinsic feature (for which the manifest means nothing). It's either that, or you want to convince people that FF the only way. No, it isn't. Deal with it.