The difficult part is to find that part of the subject, even if it's just a kernel, that triggers the interest you potentially have. This can take a while, sometimes. Perhaps reading up on how to interview people can help in this regard (it's helped me!).
In my case, but I suspect this is true for most humans, my 'genuine interest' activates once the 'human interest' angle, to put it vaguely, starts appearing. Probably because that's easier to relate to.
I hate talking about football, for example, but I've had wonderful conversations with football fans once they started sharing personal stories of things they experienced, adventures they had, or stories of how they used to go to games with their fathers, and how this was one of the few ways in which to connect with them, etc. In the process, I learned some interesting things about football too, but that wasn't really the point for me.
Over time some of these football fans became close friends of mine. We don't talk about football much nowadays, because it's clear that I find the topic mind-numbingly boring. But we do still talk about dads, and that's very valuable.
This incidentally relates to one of OP's suggestions: don't assume that you'll keep feeling the way you feel forever.
This incidentally relates to one of OP's suggestions: don't assume that you'll keep feeling the way you feel forever.