J
I definitely recommend against it specifically for painting. Even Autodesk's Sketchbook, which is free, was a much better painting program. And for the same price as Affinity, you can get Clip Studio Paint which is arguably one of the best painting apps you can use.
Now, from a design standpoint, I can say Affinity programs can replace photoshop, illustrator and indesign no problem. I've completely abandoned illustrator and indesign and I haven't for one second thought "man I wish I had the adobe product". I still use photoshop because I'm working a lot with teams that also need to use PSDs, and the Affinity Photo files can get janky when you convert them into PSDs and have someone open them in PS. If you're ever in a team environment professionally, I'd say you probably still need PS. But if you're doing just photo manipulation or print materials or design work for apps or websites, Affinity is fantastic.