To be honest when I found out about Affinity Designer, I thought I just found illustrator replacement, I've been using it for few days now, it's awesome in many aspects, like constraints, snapping and grids, it's much more better than illustrator in many aspects, BUT, it's also lacking on many ESSENTIAL features, like isolation mode, I just found out that there's no such thing in AD, and it's kind of shocking, relying on locking an unlocking layers is counter intuitive and slows the work process a lot.
Now when I find out that essentials features like isolation mode, or RTL support are requested since 2014, and still are not there... Well I can't say that AD is a replacing AI anytime soon.