Your first paragraph is like saying using email is forcing somebody to use one of a "limited set of companies". It's nonsense. Again, if they don't like what's on offer they can host their own, just like email!. They can hire a company like yours to host their credentials with as many layers of security as they want. The user has ultimate choice.

Secondly, every website on the Internet is potentially an OAuth provider.

Not to mention that I have —on multiple occasions here— suggested that websites that consume OAuth should also provide it (like Stack Exchange).