I'm not sure what little processing power you are talking about. Our RIP at times will process a file in only a minute and other times for hours on a single job. I'm pretty sure that the computers today, with most applications (some do well like Affinity and Apple), do not take advantage of the technology that has been built in to Windows or MacOS for the last 10-15 years. Waiting 5 minutes for the progress to move from 9% to 10% is not fun when you know it's just because of poor programming and the subscription model of software just enables the companies to keep it the same.
This is true. Some will make calls to APIs etc that they shouldn't need to in this day and age. MS leaves them in there, because they don't want people complaining that something is no longer working as that would affect a huge demographic for them.
It could be something like your talking about or it could be as simple as making a user run the program as admin (after installation and/or updating the program, which those should be done as admin).
Then, of course, do they take advantage of the GPU, even 2D programs can take advantage of this.
Affinity though has the advantage of being relatively "young", so what is it going to be like in 10 or more yrs? Will it to have the bloat that Ai and DRAW have now at ~30yrs or will it always be lean? By being lean, that's also going to mean certain sacrifices for the users (support for older files, certain hardware as newer versions come out etc).
I do believe that there is complacency with the subscription model on the vendors end. I unfortunately don't think that's going away in the closed source commercial world. Even programs that might offer dual licenses now, more then likely will not in the near future, especially if they are already going on that 1 yr release cadence (which is really too quick for production software, it can't have quite the beta testing that it should before release).