You know, it feels like your choice of words is counter factual even though you don't mean it. Yes, Zirkzee was the "top scorer" with 11 goals for Bologna, but that doesn't actually make him a "top" scorer. 11 goals is average. He played almost every single game that season and yes 11 goals is ok, but is that the calibre of striker that fits Manchester United's requirements to prevail in the Premier League? Seriously no, and he had some lucky moments at Bayern, which is the reason why he was eyed by Bologna. Bayern let him go without hesitation because they knew that he is not Harry Kane... Bad player and it could be easily predicted that he wouldn't turn out to be a goal scoring machine for Manchester United.
You are right, 11 goals isn't good at all and he should not be bought, not for that much money anyways. The problem United has, which I talked about before, is that if they want to buy a player, other teams charge them more. So lets say you are a smaller club, lets say you are Brest for example, and want to buy Zirzke, they ask 15 million for example, or maybe 20, but when it comes to United, suddenly that becomes 40, because teams know they can afford it.
The problem with United is that the yare not getting stars anymore, they really fail to do that and this is causing them to have failures. They need to see the world, and see which players are great, and pay top dollar to get the very best that they can afford to get. There is really no other way around it, if they keep getting these kind of players then the yare not going to get better at all. I believe Zirzkee is the best example of their problem, he was basically nobody, and they paid a lot to him, for absolutely no reason, and got no benefit. What was the point, nothing.