Piff Perkins
Veteran
If you read the OP, he's talking about legacy artists, not LEGACY ACTS. As in they can still have hits, successful tours and the possibility of new material without adhering to trends or the typical timelines for artists to stay relevant with the youth.
A legacy act is somebody who's career is in statis and people only tune into them for what is held within their legacy, little to no expectation of new material. I feel like ya'll are aguing against the latter when I don't think that's the argument that's being made.
I agree with most of your definition, I just don't think legacy artist regularly have hits the way Jay did during that period. Can legacy acts get late career hits? Sure. Aretha Franklin had a #1 hit song in 1991 for instance. But if you have multiple hits, sell a lot of records and are generally viewed as a relevant artist by fans/media/etc you aren't a legacy artist. Jay had way too much juice during WTT and BP3 for me to say he was a legacy artist.

