I'm here, which sort of makes what I'm about to say hypercritical of me, but online forums, social media are cesspits, full of extreme views. I wish they could be more civil, but heck it isn't going to change any time soon. However, use them to call out players for shocking performances etc, call them what you want (within reason obviously), discuss till your hearts content, but at the match no matter how bad it gets you should be 110% behind the team and players.
None of them will tell you they are going out and performing badly on purpose, none of them will tell you that they don't care and aren't trying. What we've got is a collection of players all playing badly, no confidence and getting no luck when playing. Booing them off, cheering them being subbed etc, isn't going to do anything but contribute to breaking a player further. I mention Brazil in my previous post, at what level is it right that a player has to hide away from his own fans when warming up to play as a sub? That's where we are getting to again, it was wrong then, and it's wrong now.
Zirkzee may never do enough on the pitch to make himself a United great/legend, but he far better than quite a few United players I've seen over the past 50 years.