Pretty much same as myself; I grew up in northern England, I've supported United since a boy, I've moved to Australia, and like you, I've been less and less engaged with the club ever since, due to a number of factors. As you say, the drive to watch and talk about football isn't there. Back home it was all we talked about, go to the pub and watch the football, talk to mates and strangers about the football. It doesn't happen here, everyone is watching and talking about AFL instead (go Richmond!). As such, I follow my footie team as much as I do United now. There's also the getting up at 1 in the morning to watch a game, the disconnect between players and fans (they're multi, multi millionaires now, back in the 80's only the very elite ended up making good money out of the game), plus the artificial financial doping rise of Chelsea and City just turned me cold to it all.
I'll still follow the results, and I'll still be pleased when United win, but it'll never ever be like it was again. Mbappe or anyone else would never compete with Eric or Robbo as a legend in my book. I don't judge anyone and if people want to win at all costs then fair enough, but I'm close to just giving up on the whole thing now in all honesty.