I have a conspiracy theory:
Adobe got a patent for plugins that work, preserve the colors and could store their state in smart object layers that may be retouched multiple times.
Serif worked around the patent: they also allow plugins, but those plugins don't actually work - the whole thing is just messed up. Problem solved!
I hope that Serif will fix integration with plugins and I hope that they will implement Live plugin filters. I can't see myself having to restart adjustments in a plugin every time from scratch. Photoshop does it really well with smart objects.
On a aside note I want to say that I am very impressed with Affinity Photo and I completely get how much work it takes.
I believe in AP and I want someone to bring healthy competition to the imaging, therefore I canceled my Adobe CC subscription and went with AP license.