There are cycles for everything. Right now the NBA lacks a charismatic superstar. Steph Curry is the closest thing to it and they haven't been what they once were. The Celtics, Cavs, and Thunder all have great teams this year, but again, lack any charisma from a casual viewer point of view. Anthony Edwards has the potential to be the next world-wide superstar, but he's only 23 yrs old. Give it a couple more years and I think you'll see ratings start to pick up again.
Lebron is a great player, but boring. Doncic is amazing to watch, but again, has very little charisma. The whole Eastern Conference is unwatchable unless you have a hometown team. The Knicks are the closest thing to something entertaining and they're borderline.
The other problem is that the stars of the league are becoming developed in the NBA, not prior to getting there. It used to be you could watch the NCAA tourney and watch freshmen, sophomores, juniors improve year over year to the point they were ready to contribute and possibly star in the pros. Now, they're there for maybe one year and then get drafted and sit on the bench for 3 years until by the time they start contributing, nobody remembers who they are. They have no brand, no cachet, and no reason for casual fans to care about them.
It may truly be up to ANT to carry the league back into prominence. Hopefully that means he'll start getting a call or two. :-)