Two things that I think are worth calling out:
1. In many ways Apple's anti-competitive behaviour on iOS/iPadOS is a blessing. It's one of the few things that keep Chromium's dominance in check. Of course, it's not great that Apple are stifling innovation like this, but consider the alternative: Chromium dominance on all platforms.
2. Why it's worth caring about this at all? So what if Chromium is the only engine, it would make things easier for developers after all. To this I say, go read some of the discussions in standard bodies(for example about FLoC). Engineers from Apple and Mozilla are largely our bastion against Google's harmful proposals for the web. Pushback from Apple and Mozilla are only relevant as long as they have market share to speak of. The recent lawsuit against Google(summary[0]) by many US states should be extremely worrying to anyone that cares about the open web and it should make handing over any more control to Google a terrifying prospect.
Mozilla maintains a list[1] of their positions on various standard suggestions that is also a useful resource.
0: https://twitter.com/fasterthanlime/status/145205393819534131...