I agree.
Obviously, there is a sizable number of people who love Braxton and Threadgill. Mosaic made those sets, and they sold out. But it's also just as true that there are fewer jazz fans of those artists.
From my perspective (as a listener), these numbers related to breadth of appeal mean nothing in terms of how important or meaningful an artists work is. Sometimes great artists sell millions and have many, many fans (Ellington); sometimes great artists sell very little and have small but dedicated audiences (too many jazz artists to name). There is no relationship between the quality of art and the breadth of its appeal. None.
But I will admit that Mosaic's decision to make sets dedicated to Joe Henderson's and Freddie Hubbard's BN material sorta bummed me out. They felt "safe." All of the music was/is readily available. When Mosaic released Blakey's Complete 1960s Jazz Messengers set in the early 90s, most of that music was not available. There was a sense of discovery, of pulling something "fresh from the vault." It was different.
Most likely, Mosaic is no longer in a place where they can produce anything other than low risk sets -- and most of the stuff from the BN vaults has been presented. I get that. Things change.