I think this is a very outdated view of the way series and streaming platform have evolved. There’s no “slot” to fill. There’s no need for universal appeal.
“The Crown” is a good example. This would never have been made into a show before streaming.
The Foundation could have been a intellectually stimulating sci-fi show that appealed a lot to a smaller audience and it still would have been successful.
As opposed to the traditional networks the time you have to build that "large" audience is insanely higher. Who knows how long streaming services will be around for.
