It can be really hard to tell whether it’s the instrument that is failing to inspire you or if you’re just not being open to its possibilities. An especially easy trap for me to fall into is to think that the only way to use a piece of gear is what you hear everyone else doing with it. That especially applies to the Syntakt, I think, both because of the particular character of its sounds and the fact that it’s a new instrument that still has a lot of undiscovered territory to be found.
I’ve already sold and re-bought the Syntakt once, and I think I’m keeping it. I’m not the biggest fan of most of the music I’ve heard other folks make with it, I’ve actually made a few things with it that I really like. And that’s what matters!
So, IMHO it’s really on you to decide whether and why to keep it. The only advice I would give is to not worry about it too much. Make a choice and don’t stress. If you need the money, sell it. Or put it away for a while if you can afford to.
If you want some evidence that it can do non-industrial stuff, here’s a silly January thing I made this year that is…well, not industrial, I think.