The MM extension did help some aircraft, but it did not solve anything for aircraft now of BR from 11.3 to 12.0. They’re stating uptiers, while for example the F-14A on 12.3, which even in the old MM had practically only downtiers, has matchmaking in 90% downtier again. Aircraft on BR 12.0 can still deal with it somehow, but aircraft on 11.3 have absolutely no chance against aircraft on BR 12.0 and 12.3. It’s a total disruption.
It doesn’t matter that you have a seemingly acceptable BR 11.3 when you spend almost 100% of your battles with 12.0 and 12.3 aircraft. It’s not that bad with 12.0s, the vast majority of battles are against F-14As on 12.3s, but it’s still uptier in practically every battle.