As someone who has played both horde and alliance in shadowlands lfg is different.
I’m not saying that there aren’t good players on alliance, the faction as a whole doesn’t focus on endgame as much as I have seen on horde.
Lfg is slimmer on alliance and the groups I did pug were a struggle just to time 15s.
Yet I swap back to horde and people time 15s without even talking in party.
It’s al it’s just an atmosphere I want to say. Most people who play endgame in any serious setting are better off going horde.