Same here. Affinity is great, it has some quirk and some basic features are scattered around the UI without seemingly much thought.

But every time I have to use Gimp is just a pain, feels like going back in time.

For such a complex tool, UX is and will always remain king. That's why many people miss even something as simple as the Mac Preview tool, it does its job nicely and neatly. It doesn't do much but for basic stuff is quick and straightforward.