It breaks the suspension of disbelief. There is one Klingon serving in Star Fleet: Commander Worf; plus a human-klingon half-breed in B'Lennna. There are no Romulans. There was one former Borg (Seven of Nine). There was one human-Q that didn't know she was a Q, and she wasn't in Star Fleet. El Aurians are very few in number (compared to other Star Trek races) and (to the best of my knowledge) we have never seen one in Star Fleet.
What you are doing with your cast is throwing away these races rarity (and uniqueness) and cramming them all aboard the same ship. Why? If you story is a good one, does it really need this highly eclectic and varied racial crew? Where are the Efrosians, the Caitans, the Tellarites, the Andorians, the Deltans, the Bolians, the huge number of other Federation member races?
It defies the imagination that a single ship would have the cast that you have assembled. That is what is wrong with your crew.