Would you have preferred Luke to be more involved?
http://i.imgur.com/8AJdGYS.jpg
They were concerned Luke would upstage everyone. But how would you have felt if for example Kylo godstomped Rey and Finn and then Luke rescued them, AOTCs Yoda style?
I think it would have added a bit of credibility to Kylo + a ton of emotional stakes after he killed Han and was his apprentice at one point.