I don't believe our players are that shit at crossing, I genuinely think it's the system. Our players look clueless as to where to cross, and our forwards don't know where to be to receive those crosses. Are we going near post? Back post? Drilled? Floated? Into space? At feet? Cutting back? If the cross doesn't find its way, who is designated to pick up the second balls in each of these scenarios. The only semblence of a plan is when Fellaini is on pitch, and that's why Mourinho loves him so much.
You could get in Beckham into this team, and we still wouldn't find headers from free kicks or corners, because no one has an idea where to ping these crosses or where to be to receive them. It's too random.