The NBA promotes the WNBA. Not sure what would be enough for those that think the NBA doesn't do enough but EYE think they promote it enough. They promote it more than they promote the G-League for sure.
Like
marikomorose
said, there is just too much of a gap in what men and women PRO basketball players can do for the WNBA to reach the heights that people are hoping for.
NCAA sports are different because schools have decades upon decades of alumni, boosters, parents, and former Athletes as fans. The WNBA doesn't have that luxury so NCAA women's basketball has more of a shot of reaching at least a fraction of the viewership as the men's game. ( Aside from the NCAA Tournament, the gap is still HUGE. SO don't be fooled)
It isn't golf, tennis, futbol, or gymnastics so the WNBA will always suffer.