I recently heard an interesting podcast about the definition of legacy software. i agree that the attribute that we put onto a piece of software and marked one as legacy is a debatable one. The definition is subjective and comes from personal values.

Is a piece of software becomes legacy as newer technology arise?
Is a piece of software becomes legacy as the authors moved on from the team?
Is a piece of software becomes legacy as we learn better technique and practices.

Those values we often use as yard sticks to which then we apply the 'legacy' attribute to a piece of software. Which soon after, we often look back at it as a mental burden, a personal anchor to our creativity.

From a state thinking that a piece of code is a masterpiece, to 'I could've done that better', which finally lead to 'This is something that I can't work with'.