That's true, I'm mostly pissed about Apple locking down the iOS browser ecosystem, which is not the case on macOS.
While I think Firefox and Chrome did not have a level playing field especially the release of the M1, because Apple has started optimizing Safari for their arm64 platform for example way earlier than FF/Chrome even could. Also, obviously, Safari can focus on a single OS while Chrome/Firefox has a lot more to manage here. But I mean, that's not Apples fault.
Still, while I also experienced the problems you referenced with Firefox on my M1 for months or a year, it has greatly improved and IMO is at this point on par with Safari. With the plus of being open, having a huge community and heavy customization options, and privacy. But with the minus of being ugly in comparison to Safari, I must say.
So yeah I mostly am in line with your opinion, apart from one thing:
> so it's not like there's all that much competition.
This, at least this is my opionion, is no argument. It's playing down the importance of free choice IMO. It should not be more okay to disallow alternative browsers based on the existence of alternatives. I mean, if they never allow it, there will never be any. We can just hope that at some point some competitors will rise again, maybe Firefox will get a bigger foothold, or Ladybird, or Servo, or whatever. I'm just trying to keep my hopes high here, haha.