I learned that from Microsoft: all of their competitors products were, from their perspective, a legacy system off of which you were almost-by-definition migrating to a Microsoft replacement (and if you weren't, you de facto weren't their customer).

The difference between the connotations of the word “legacy” in general and inside the tech industry is worth a ponder.

Fundamentally, legacy is something left to us by someone else. On its own it’s neutral: if it is a result of someone’s effort, legacy is usually good; if it is a result of someone’s mismanagement, legacy is bad.

Curiously enough, in tech the mere state of being left by someone always implies something undesirable, obsolete, to be replaced. No matter how hard someone worked on it, where there’s legacy there is a tinge of exasperation. The state of being legacy is more or less an opposite to being current; a piece of software cannot be both.