Save up and invest. Become independently rich. Doing boring, pointless, mind-numbing projects like those you described, is the best way to do it because you can

Save up and invest. Become independently rich. Doing boring, pointless, mind-numbing projects like those you described, is the best way to do it because you can charge top dollar, as most smart guys won't do it, they want to do sexy things, so your average competition is quite dumb, and those projects make clients a lot so they are willing to pay for not-quite-dumb developers. And you can do many of them because they aren't too tiring. Then even if you never achieve professional self-fulfilment, your kids will never need to work and that alone can give a whole damn lot of self-fulfilment to you.