Your experience is starkly different than mine. Are you sure you aren’t thinking of Pixelmator, Pixelmator Pro’s much more toy-like predecessor from ~10 years ago?

My experience is that while there’s a feature and community gap for both Pixelmator Pro and Affinity, Affinity just tried to copy Photoshop, positioning it as a worse but cheaper Photoshop, while Pixelmator Pro feels like an attempt to make a better photo editor, losing some familiarity points but also being tangibly better than Photoshop at most use cases it can handle, which is many. It’s also an excellent macOS citizen. Between those two factors, it seems much more up Apple’s alley.

I guess it depends a lot on the use cases. I've used both the original Pixelmator app and the "Pro" may have been a rewrite internally but it didn't feel like a significant step up for me at the time, more like a rebrand and a way to charge for it again. And so many bugs. The development team did respond to a few of my bug reports, which was nice.