Well crap, I'm in my second go-around as startup CTO (and I definitely want to do more), so I guess I'm doing something wrong because I've loved every minute of each startup.
I think the big thing that makes all the work and stress worth it for me is that these are projects I would volunteer for with or without pay. Last time it was a fitness network that helped people develop a sustainable healthy lifestyle. This time it is shaving 10-20% off the installed price of distributed solar. Got way past the MVP stage last time (over a million users), and close to getting there this time (more business LOIs coming in every day).
I love being a technical cofounder. My skills are technical, so I can contribute the most in that role. But the startup has to be something I would volunteer for. So I guess you're right, startups don't find me. I find them.