Layering is “at fault”, but not in the context of people blaming layer hopping and layer abuse. I think intentionally “gaming the system” with layering is a very small percentage of effect on the economy.
Instead, think about how Blizzard has stated a "Low " population realm in Classic has more players on it than a “High” population realm did back in vanilla.
Source: Overcrowded Realm Update
Since the only way Blizzard could deal with such an immense population is layering, this means each layer is another entire server’s worth of item drops/gathering resources for that server’s single economy. Even if everyone was absolutely honest and never abused layering, you have several servers worth of resources being obtained day-in-day out.
Server economies will continue to see inflated item availability until layering can be disabled. That said, I still think layering is necessary to allow for the long-term population health of a server.