Have you considered the possibility that you're actually clinically depressed? Working on the assumption you are male, I think a lot of guys don't realise that low-grade depression looks like this for a lot of us. Especially getting towards mid-life.
One thing I would suggest is to embrace boredom. Cover up your television, delete your streaming video apps, cut back on social media as much as is possible, stop gaming if you game. Stop avoiding boredom with low-energy solutions.
Get really, really bored. Then see what your brain wants you to do. Boredom is a precursor to a creative state.
Another thought: consider if your "worthwhile" is actually helping other people do theirs? If you can learn new tools and languages easily, could you help others? Could you teach?
I need this change in my life too, and this is the direction I hope my life is heading in.