This is a version of one of the killer questions that is supposed to show the RBE as flawed, but the best is the eneny of the good here.
In the current system if something's abundant it's a problem, because it's hard, if not impossible, to make money out of something that's abundant. This is why food is wasted or stockpiled while people starve to death, and why [alleged] natural cures for illnesses are downplayed, denied, hushed up or exproprited as commercial products. It cannot be any other way with the current system.
An RBE addresses this issue of deliberate scarcity. Yes it is left with actual, irreducible scarcity, but to use that as an argument against it is invalid if it means sticking with the system we've got until we find a flawless replacement.
We don't really know what these irreducible scarcities are, but we certainly know what the avoidable ones are and I say we make a start.