Well, they made them more plot relevant with the fact that they were chosen to be the next Reaper, but I don't see how they're perfect or idea. Also, they were already special in ME. Their rise in the galactic community was something no species previously did. They gained a embassy (and Spectre) and at least a seat in no time, they co-created a really advanced ship, and they saved the Citadel. They were already the galaxy superstars.
Also the fact that the focus is on humanity doesn't mean the'd be perfect or ideal in Andromeda.
Oh come on don't be so naive. The Reapers did not write Mass Effect 2, Bioware did. Bioware did not HAVE to make ME2 be all about Human's being the saviors of the galaxy which essentially what happened in ME2 and especially ME3.
Bioware did not HAVE to make Earth or "take back Earth" the main theme of ME3. Why not take back the galaxy? Why the focus on Earth? I thought the Reapers where a threat to ALL life in the galaxy? This was the vibe I got in ME1 but fast forward to ME3, it was mainly about taking back Earth with all the other homeworlds just be remote problems.
One good thing I can say about the Dragon Age series is that despite Humans being the political, social, economical, and even military power in Thedas, the game stories never make it out to have Human's as the main saviors. But with ME2 and ME3, it is ALL about humanity and how powerful they are and how much of a threat they are to the Reapers and how it will be up to them to save the galaxy.
I just hope that MEA is a story about ALL species endeavor to find new hope beyond the milky way....but just told through a human lens rather than a story about HUMANS endeavor to find new hope beyond the milky way.