Maybe I'm naive, but what stops indie studios from creating cinematic universes? The props, sets, visual effects, etc. are primarily what's expensive, not the size of the (in-your-head) universe. If anything, I would expect indie universes to be more consistent and to have more meaningful/powerful plots, because these things tend to be labors of love rather than the more cookie cutter process we see in the big films.

I think the big thing is the financial risk of committing to a series, but it seems like if you take the films one at a time, you get to see how the last one is doing before you get too far along making the next one. Can't be that much worse than making everything a one-off.