If it is demonstrated that spacetime is not fundamental, it would indeed have profound implications for our understanding of gravity. Spacetime is a central concept in general relativity, where gravity is described as the curvature of spacetime. If spacetime is not fundamental, it would suggest that our current understanding of gravity needs to be revised.
In such a scenario, the problems associated with reconciling gravity with quantum mechanics, known as the quantum gravity problem, would likely take on a different form. Quantum gravity seeks to provide a consistent framework that unifies gravity with quantum mechanics, and it assumes the existence of a fundamental gravitational interaction mediated by gravitons.
If spacetime is not fundamental, it may require a more radical departure from our current theories and a new approach to quantum gravity. This could involve describing gravity in terms of emergent phenomena or alternative fundamental building blocks that are not based on the concept of spacetime as we currently understand it.
Regarding the hierarchy problem, which refers to the large discrepancy between the weak scale (the energy scale associated with the weak nuclear force) and the Planck scale (the energy scale associated with gravity), it is primarily a challenge within the framework of the Standard Model of particle physics and general relativity. It arises from the vast difference in energy scales between the forces and is related to the question of why the Higgs boson's mass is much smaller than the Planck mass.
If gravity is not fundamental, it is possible that the hierarchy problem may be addressed in a different way, depending on the specific nature of the underlying theory. However, it is difficult to make definitive statements without a concrete understanding of the fundamental nature of gravity and spacetime beyond our current theories.