This is what I've been wondering about. I don't care if the stack isn't the newest, or the tech is the shiniest. I'm just more interested in working on code that was _engineered_. That is code that was designed and then built. That's the problem I have with most of the code I'm working in.
At my current place of work, we're not even using xmlhttprequest. We're using an antiquated xml library that's been hand rolled (xajax + major changes) to emulate our ajax requests. It's insanity to me that we're still in this mode.
I would agree that if all you work on is greenfield you're probably making the messes others are cleaning up, but I don't think that means developers are bound to either make messes or clean them up. There are plenty of good, long-lived projects out there.
Not every old project is legacy.