On the contrary. An assembly for Yorkshire, for example, would be much more responsive to needs within the region than Westminster would be. After all, Leeds has completely different needs to a fishing village in Sussex. I don't disagree that we need to give assemblies much more power, including fiscal powers, as well as giving much more power to local councils as well. All power belongs at the lowest possible level - bottom up is the answer, not top down.
I shall remember this when the Loony left becomes a thing.