The Blunt Instrument answers questions about the necessity of an MFA and how well-networked a writer must be to succeed. Among other things, he says,

Writing and reading and doing the rest of the administrative work required to get published take up a lot of time, most of which is uncompensated, especially at first.

You can do all of this (find a community, carve out dedicated writing time, etc.) without getting an MFA, but an MFA is a structured system that makes these things easier to achieve in a short time period. In my opinion, that’s what you’re paying for, more than the largely useless degree.