Lukaku is blessed to have been given even the glimpse of an opportunity at a club like United considering his limitations. For him to think for a second that he somehow deserves better is completely baffling to me.
Look at the long list of better footballers and forwards who have spent time being second choice or worse at this club:
Solskjaer, Forlan, Berbatov, Saha, Sheringham, Yorke, Tevez, Hughes just off the top of my head are all vastly superior to that lumbering oaf and all of them played honourably in our shirt, taking their chances when they got them, even while spending large periods on the bench.
Being able to control basic passes isn't a specialised skill for a footballer. Managing to keep possession for more than 3 seconds shouldn't be either. Spend more time on the training pitch, work harder to improve on your weaknesses and offer something of use to a club you should never have been allowed dream of joining rather than throwing your toys out of the pram and flouncing to an easier league under some notion that you're a superstar.