A lot of the older community talent, particularly in music, was vetted by the community/grassroots with associated infrastructure; in other words, a community center of gravity. This is where you get terms like "black famous vs hollywood famous". When we rely on hollywood for all process of talent promotion (from education/training, to promotion), you have a botteneck where only a few get promoted at one time. This means entire culture/arts forms are simply not being created and disseminated; there simply are no grassroots pipelines or vetting/validation mechanisms***. Hollywood was never going to create Motown, etc, it had to be done at the grassroots level. This same dynamic is true today. Hollywood is an industry that sells culture. It is not the raw culture itself.
***I.E. compare the sheer diversity/culture we had with 60s, 70s labels, etc compared to after they were absorbed by Hollywood. Or just the past musical scene compared to today. Essentially like comparing a specialty store to a mere shelf in a supermarket. Mainstream assimilation is good for individual artists, but potentially bad for any distinct broader cultural group, because there will never be a 1:1 integration. Things will get left behind, watered down, distorted, appropriated, etc. You run the risk of participating in a caricature or monolithized version of your own culture, or even getting Elvised at worst. The goal should be to continously empower a distinct center of gravity that can then project outwards on its own terms. This base of power could then exist within the broader mainstream environment without compormising itself.
It should give pause when people say 'when is hollywood going to do x, or y for us', when they understand the implications of such co-dependency. A person of sound mind would be wary of Hollywood (or any external paradigm) having any say in their representation, not running into its arms. Once you see things from that perspective, co-dependecy is like a state of learned helplessness.