Niko does have some ego sure, but I think he's getting too much blame/hate.
Sure he wasn't good on the AWP, not as MAIN AWP at least. But was it HIS decision to play that role? I believe it was G2 who suggested it, and he wasn't afraid to give it a try. I think a lot of people put every decision (especially the bad ones) on Niko's shoulders as if he controls everything.
He's a top level player, star player, but he's supposed to play in his main role, to really shine.