I could be wrong but I have been under an impression that angelicus exhibit some variation in appearance, some have black base, some brown, some cream colored spots, some white, so the contrast and the color depth varies. Maybe you are right, it is the age thing. My old one looked the same. But I recall seeing photos of large ones that looked better, white spots on black skin.
My Angie can be seen here in some of the photos:
https://www.planetcatfish.com/forum/viewtopic.php?f=2&t=30939&hilit=120+gal