I disagree that it's a niche, he's just doing a good rounded job in midfield.
Not going to sit here and tell anyone Xhaka is perfect, but there's two things to bear in mind. First is that anytime he's had a half decent partner he has looked good, Torreira for spells and now with Ceballos. Partner him with substandard players and guys like Ozil and he the spotlight falls on what he can't do.
Second is that his game off the ball is superb. He times his presses well, prepositionally he's very good and he's always available for a pass - Arteta has really helped get his body shape right to receive a pass too so it gets stuck under his feet a lot less - it all lends to why he gives the side so much structure.
There's some games where we need a quicker tempo and more creativity where we'd be able to drop him, but if we're playing with 3 midfielders going forward he needs to be a part of a core group of 4 midfielders who we can depend on.