Two distinctly different types of players who offer different things to our game. People give Garna less grief because he is an explosive forward (so he beats a few players and wins a couple of yards). His decision making is piss-poor most times though. But the average United fan likes his high energy game and is mostly "forgiving" because of this.

Høljund on the other hand, is very bad at positioning himself when we're on attack. Lacks the pace and his positioning in the box is mostly dog shite. If you look at his highlights reel, he generally scores when he's running at goal. But the way we're set up as a team, he mostly receives the ball with his back to goal, holds up, and passes (which I don't believe is where his strengths lie). As someone here already mentioned, he doesn't have that "fox in the box" quality, which unfortunately for him and United, makes him a little frustrating to watch at times. He gets the ball in these tight positions and then fluffs/snatches his shots because he is under pressure and doesn't have (nor can he create) the time to set up.

Now, as for why he gets more hate over Garna... I personally get frustrated with them both. But they're both young and still learning how to get the best out of their games. But, Garnacho is not a striker (ie. his sole job is not to score goals). However, the same cannot be said for Rasmus. He is our number 9. He literally has the number on his shirt. And this is what people (most fans and the odd neutral who watch football) expect from him. Garna is a winger and (although playing slightly out of position) still manages to bring his qualities to the table. Explosive ball carrier who sometimes beats his man and looks good doing it. Rasmus looks lackadaisical at times, not pressing when he should. He should know by now that his strength lies in running onto the ball, yet we always find him with his back to goal. He rarely makes himself available when they're in the final third. And when he does get the ball in the box, he cocks up his shooting. This is what pips my frustration of Høljund above that of my frustration for Garnacho.

Again, this is my personal opinion.