My personal feeling about Eno's approach is that it almost deserves a different label than "composing" - maybe "incubating" (you know, like a startup incubator). For me, and I suspect for a great many music lovers, "composing" implies a process that may be evolutionary to some degree but is still overseen and directed from beginning to end by a particular artist. Contrast that with the case of traditional music from $REGIONAL_CULTURE where the process is more truly evolutionary as songs are passed from one generation of bards to another.
(I don't mean to say that Eno's approach to making music is somehow less legitimate than any other. It just seems better described by some other word.)
I think you make a very good point - which is that in the bigger picture, music is inherently evolutionary in a way that generative music isn't.
Having some experience with generative apps, I know that they absolutely do not make music spontaneously. You have to invent them, build them, and tune them - all by hand/ear.
It's more like building an instrument - i.e. a machine - and tuning/debugging it than cultivating a garden.
Music as a whole is much more free. When it's loose in a culture, it can evolve in weird, unexpected directions that no individual composer would ever be able to imagine, and no app today would come close to copying.
I'm a couple of years into playing with generative music, and one of my big problems is finding prior art to imitate...
The problem is when guys like Eno talk, we dismiss it as a little obvious and perhaps a little old fashioned, only because we're so much past that and largely due to guys like him. A bit like reading about what computer geeks were excited about in the 80s and chuckling a little how simplistic or ordinary it seems now. Back then, it was cutting edge thinking.
I also feel this has given listeners a narrow and unrealistic view of what music actually is. For example, complaining if the lead guitarist in concert doesn't play the guitar solo from the record note-for-note, even though that player improvised the studio solo and might have real difficulty replicating it - not to mention little interest in doing so.
This also leads to the phenomenon of "cover bands" that simply do live note-for-note versions of someone else's record. As a musician, the idea of doing that seems utterly bizarre to me, but it's obviously popular!
Also to your first point, DAW software is now akin to a canvas and recording can also be part of the creative process. I used to try to record in stages, write, rehearse, record, produce, master. Now I find that I'm kind of doing it all at once and the results don't end up any worse except for one thing. The compositions are usually less complicated without having the time to think about it and practice it.