Well yes, exactly. The 'realism' of Starfleet's oddly human make-up is irrelevant - aliens in Star Trek exist to cause a problem for our heroes to solve, or to serve as an allegory to make a point, or both. Even the aliens we get on the main cast fulfill the 'looking at humanity through a different perspective' thing. This use of aliens naturally means that Trek will largely feature humans to be observed or to interact with.
The alternative approach, aliens are humans with bumpy heads, who act almost entirely as human characters apart from makeup, that you see on, say, Farscape, has never been Trek's way. Generally, each alien race comes with a quirk, a perspective, or a trait that is exaggerated to make a point.
