> Everything I do day-to-day is either stuff that I need to do to pay the bills and support my family

That's the universal trap.

> people like Feynman are born with a burning passion for learning that most people just don't have.

I am not sure about that. I'd say most people lose sight of their true passion. Mine happened to be programming, which now helps me pay my bills. But I'd be screwed if my true passion was drawing...

Wait, I used to love drawing, until I took drawing "lessons".

> Now, at halfway through my 50s, I would not be able to answer the standard interview question "what are you passionate about?"

I once heard this logic which did guide me a lot : if you were older (say 80), what would yo regret not having even tried ? If you haven't even tried, let's try.