[derefr]

"Can't quite understand" in an intellectual sense (i.e. "where they're coming from" or "how they think"), or an emotional sense (i.e. "what they're feeling" or "what they want")?

I can perfectly-well understand being content with the first kind of disconnect—that's the kind of puzzle that drives you to learn more about your partner.

The second kind seems a lot more fundamental, though: if someone had completely different preferences or feelings from me, to the point where I couldn't even understand those feelings/preferences, I'd just feel like they were an alien.

And I mean, maybe I'm imagining something too far out-there; I can perfectly well understand the feelings and preferences of e.g. autistics or sociopaths or narcissists. But, say—someone who enjoys things, but then this enjoyment doesn't translate to doing those things ever again? Can't connect. Just don't get it. Bizarre alien mind architecture.