I'm not from England, so take this with a pinch of salt.
I started supporting United because of David Beckham, and SAF and the CO92. I see them as the protagonist, the football billionaire everyone hates for being successful, the good underdog that are fighting to surpass Liverpool and knock them off their fecking perch. The one that rises through the ashes of Munich, never forgotten. The one that always scores, and the one that reaches the promised land.
Trophies are secondaries, I would have still supported us even if we fail at the treble, no biggies.
But I find it hard to root for the current team, they are everything that the 90s United are not. Seeing bunch of prickmadonnas like Rashford, Shaw, Pogba, even seeing the likes of Ole who's managing abysmally and only being given the position because of nepotism, seeing the likes of Maguire, and Rashford giving fans some fingers (something which will never be tolerated under SAF), this is not the United I sign up for. And title / trophies has nothing to do with it, I'd gladly support the team if they have a bunch of likeable players who plays for the shirt, sweat and come short.
And you can say it's a cardinal sin etc, but I really find it hard to motivate myself to root for this team.
Would I ever support another team? Nope.
Would I root for this United team? Finding it very hard.
Maybe one day, when we finally got a set of players that ticks my box I'd be rejuvenated, but as this point.. i'm indifferent.