I don't believe anyone can go it alone...that doesn't mean everyone has to be in a group recovery program...just that we need other people in our lives, we need connection.
And whether or not we are dicussing recovery with the people in our lives, we NEED them and the relationships we have with them in order to recover. No one lives in a vacuum.
Also, to recover as opposed to just stop using, we are going to have to make other changes in our lives and how we operate and deal with people and situations, that is going to shake up our relationships, and having the people we care about work with us, rather than resist all changes is a huge help in recovering.
so, yeah, lots of people do it without 12 step or therapy or whatever, but no one really does it totally alone.