I’ve seen many more people say something rubbish like this, so here I am, tossing my two cents.
Dickfaces, here’s a news flash, you don’t have to play the game, you know. You choose to. So if you’re getting “tired of playing as Ezio Auditore”, why don’t you just quit, huh? Nobody forces you to play it. And if you’re now going to whine about how you want to know what happens in the main plot or the universe or whatever bullshit, then I say to you: there are plenty of walk- and playthroughs on YouTube and where-ever. Go watch those. Or go read a Wikipedia article. There’s also an Assassin’s Creed Wikia out, did you know that?
Second of all, it’s not really a coincidence that out of the four games so far, three are mainly about Ezio. Subject 16 was forced, by Abstergo Industries, to relive the memories of his ancestor, Ezio Auditore, who the Templars knew had located the Vault during his lifetime. Then, as you may or may not recall, Subject 16 kind of killed himself, thus leaving the Templars without the location of the Vault. However, they learned of another Assassin - Altaïr, of course - had once held a Piece of Eden.
It’s a fact: Ezio was Abstergo’s/the Templar’s first interest. Not Altaïr. So it’s only natural that three out of four games involve him.
So do you have reason to whine? No. Not really. There are plenty of other games out there (95% not even worth playing compared to this, but whatever, that’s just my opinion) that you can play instead of this, with a lot of undeveloped, shallow and perhaps more interesting characters for you.
Hands down. Ezio is badass and if you’re tired of playing him, then you’ve just got nothing better to whine about.