Lot of interesting answers here.
To elaborate more for myself, just going through different genres was my main thing. Most of what I do now would likely be most similar to New Age influence; I guess when I think about it, I've wound up combining most of the previous genres I was fixated on into one. Orchestral elements, folk elements, and usually some form of band/rhythm section with a focus on melody and real or sampled acoustic instruments. It comes out sounding like Loreena McKennit, Yanni and a lot classic soundtrack music from the good ol' days, if I may be so bold.
I actually think the very process of getting older is mostly what has motivated these changes; I know it's a cardinal sin to say you "grew out of" metal, but I really think that's what happened. I remember when I was 24 or so, a friend asked me if I wanted to play guitar for some live shows in his cover band playing rock music and rock arrangements of video game music. I declined and I came to realize that the reason was that, even though I still like the music and do write the odd electric-guitar song here and there, there's just no way I could get up on that stage and pretend I'm 16 again. I do think that, with certain popular music genres, there is an inherently youthful aspect and not too long after it becomes cringe and perhaps even undignified; look at Stephen Pearcy from Ratt. The man is in his 60s, still covered in tattoos, drunk all the time, and up on stage bumbling around still trying to belt out some song about girls and partying like he's still 20 years old and I'm sure that, in his mind, for that hour and half he's back on stage — he is.
But yeah, other than that, I can't really stand electronic instruments and synthesizers anymore. What I like about acoustic instruments is that if you have a good room, a good instrument and a good player, you can basically just put a mic in front of them and let them fly at it and it just works; it sounds exactly like you'd hoped and expected.
But creating a good synth patch and getting a good distorted guitar tone — I'd say for every 10 electric guitar tones, there are 9 bad ones — are arts unto themselves and very time consuming. A teacher of mine used to say that every minute you're screwing around with knobs and tackling learning curves, you're not making music.
That leads me to the other thing that's changed: I just want to make music; not screw around with knobs, mic placements, technology etc. to get the sound I want.