>>11044479This is actually incorrect. It's true that, from an effective point of view, there can always be a larger energy scale the physics of which decouples from that of our current theory. The way this energy hierarchy is segregated is with the spectrum of the theory. If the spectral gap for a theory grows with the RG flow, the physics at the IR fixed point for the two spectral "islands" decouple and an effective field theory, describing only the low-lying spectrum, can be constructed.
Now if the spectral gap all remain constant even at the IR fixed point, we then have absolutely no definitive energy scale at which we can make our "effective" distinction. String theory, being a CFT, is an example where this occurs; all primaries increase eigenvalues by a fixed discrete value, and all conformal descendants can do is shift the Verma modules around. This means that there is no inherent energy scale to string theory, and if it truly is an effective theory then its "parent" theory must have a spectrum , where one of the gaps suddenly start to increase without breaking any symmetry or lifting any degeneracy. At the very least with our current understanding, this is absurd.
