I think your experience matches what 99.999% of engineers feel. Very, very few people get to ride a cool tech wave. John Carmack got to make a living making Doo

I think your experience matches what 99.999% of engineers feel. Very, very few people get to ride a cool tech wave. John Carmack got to make a living making Doom and Quake. Good for him. For every John Carmack, there were tens of thousands who tried and failed at game dev, and ultimately went back to their day job making accounting software. Because, as you say, most of the time business and marketing make things successful, not the actual tech. Only rarely does a hard-working programmer make something at the right moment that catapults them to success. But that said, I don't think that fulfillment in tech is all or nothing. If you work very hard on a side project, you may be able to capture a tiny amount of success. Maybe your side project can generate enough money to pay for coffee every month? That would still feel pretty nice.