I also find amusing that “legacy” more often than not gets used in negative conotation. I hear “legacy” and I think “bunch of people wrote some AWESOME shit that lasted so long that now other people get to view it as ‘legacy’”
It's probably used in the (now) classic sense as defined by M. Feathers in his "Working with legacy code" book.
Code that is old but otherwise awesome, maintainable (or even actively maintained) and easy / a joy to work with are rarely referred to as "legacy code".
But you will quickly learn how awesome the old code base is if you attempt to rewrite it, and realize everything the old code base takes into account.