Netflix had a near monopoly on the streaming but not on the actual shows and movies. All the studios still owned their shows and movies and could unilaterally pull them off Netflix and make their own services, evidenced by the fact that that's exactly what they did. Importantly, the monopoly was not vertically integrated. Similarly, Valve makes very few of the games available on Steam.

Streaming will not get better as the studios fully monopolize it. Not without at the very least and most liberal an enforced ban on vertical integration in visual media and on exclusive licensing agreements. That won't happen under capitalism though, so the only real improvement will be in the resurgence of piracy.