I'm not really referring to in-game achievements as a legacy - it is remarkable when a community of any type keeps it together for a decade and a half. Like many, I've made and lost entire groups of real life friends in far less time than that. When I talk about legacy in this case, I am referring to what I mentioned in the second point of my post which was
Building a lasting community with people you like that stands the test of time is its own kind of legacy, irrespective of wins and losses.