I don't know enough about the DC cosmology, but I suspect it's not the case, the Outer Planes are not only the domains of the gods in the Great Wheel, and some gods don't even dwell there anyway.
You can have a look
here, it will show you that it is really a multiverse and not only planets in a galaxy (some of his other series like skywards are not in the cosmere and are in the galaxy though). But it is a multiverse, and a very complex metaphysical one with three realms (Physical, Cognitive and Spiritual) interfering, and it's probably not all as there are also things beyond death not covered by those realms.
Because they behave differently and cover a physical transition and a metaphysical one. One would be more boring and less rich, and honestly "speed force" is a concept that does not make any sense for either, at least to me.
My point is that simplification for the sake of simplification is pointless, designing from the ground up is way better if it matches your goals.
It depends on your point of view, for me the success is very relative in the sense that I'm not interested in it at all for my TTRPGs (contrary to the Great Wheel, or even better to Glorantha).