The eye opener is that right now our players are a bit overrated.
The only player of ours who has proved anything at any level is Pogba, and even he is a doubt. What hope do the likes of Rashford, Fernandes, and Martial have to get in over Lewandowski, Muller and Gnabry? Of course there's the implication that in a working system they'll shine as well, but until that's proven, none of ours is getting into a treble winning team.
With that said, no reason that can't change over time. With more experience and maturity our strikers especially will get better, and who knows how their careers will pan out.