I do find periods during which I'm not really interested in things to be frustrating and somewhat depressing. Another thing I run into is I get into an interest and I have no real way to do much with it other than research on the internet (which is informative, but less satisfying than, say, buying the books and watching the documentaries, etc).
My primary interest is gaming - usually specific games or specific publishers. It's kind of strange to me that my interests tend to be fairly popular as when I first got into these kinds of games, they were a very very niche hobby. The way games work has shifted too, which tends to leave me adrift more often and I go back to the older paper games I like versus the newer video games.
I think I'm kind of drifting now, mainly because I can only really engage in my secondary interests and can't pursue my primary interest. It feels kind of like anhedonia, which makes me wonder if there is actual depression on the way, but I'll find out tomorrow when I can again pursue my primary interest properly - by which I mean not just playing the games, but researching the background, numbers, etc. Mostly I'm waiting for new games to come out, so anything I do is research more than playing anything. If I'm really interested in a game, I probably spend about 75%+ of my time modding it, researching it, talking about it, etc. and relatively little actually playing it.
It also doesn't help that video games are overloading, and if I play one for very long a shutdown is virtually guaranteed. Doesn't stop me, but it does slow things down. I still play them because unlike those old paper games, I don't generally need other players to enjoy video games.