A New Equivalence Principle

If we want to revolutionize physics, by creating a GUT of Quantum-Gravity, wouldn't be a good idea to look at the past examples of revolutions in physics, first?

For example, how Einstein and Newton did it?
(Their success was really due to their superior (to everyone else) mathematical talents?)

I think, in Einstein's Special Relativity Theory case, a big experiment (Michelson–Morley Experiment) disagreed with Newton Physics.
And unlike other physicists, Einstein fully accepted the results/implications of the experiment, which (its mathematical expression(s)) led directly to Special Relativity Theory!

When it comes to Quantum-Gravity Theory problem, do we really have any big experiment disagreeing with Quantum Mechanics and/or Relativity?
I think the answer is no!

I think, in Einstein's General Relativity Theory case, on the other hand, Einstein started with finding/defining a new (real/physical) Equivalence Principle (equivalence of gravity and acceleration), which (its mathematical expression(s)) led directly to General Relativity Theory!

I think, what led Newton to success was also finding/defining a new (real/physical) Equivalence Principle (equivalence of force between, Earth and a falling Apple, and, Earth and (constantly falling) Moon)!

Can we really find/define a new Equivalence Principle, to led us to a (realistic/consistent) GUT of Quantum-Gravity?
A new (real/physical) Equivalence Principle that joins/bridges foundations of (General) Relativity and Quantum Mechanics?

Can't we say foundation of (General) Relativity is spacetime?
Can't we say foundation of Quantum Mechanics is quantum-vacuum?

Then, what if, we define a new Equivalence Principle, such as, spacetime and quantum-vacuum are equivalent (same)?!
Or, spacetime is created by quantum-vacuum (which created by virtual particles keep popping in and out of existence everywhere)?

Consider that, how air around us looks like empty space, but we know that, it is actually a (transparent) gas medium, created by atoms/molecules.
Imagine that, quantum-vacuum was also similar, a (transparent) gas-like medium, created by virtual particles keep popping in and out of existence everywhere!

But, if spacetime is actually quantum-vacuum, (when quantum-vacuum observed from macro-scale), then, what really is gravitational field?
What happens at micro-scale, to quantum-vacuum (medium of virtual particles), when we see (positive or negative) bent spacetime, at macro-scale?
To answer, imagine that, if we observe flat spacetime at macro-scale, then at (quantum-vacuum) micro-scale, average probabilities of, positive energy/mass virtual particles randomly coming to existence, and, negative energy/mass virtual particles randomly coming to existence, are equal/balanced!

But, can we really say, we have perfect/absolute/clear justification to define/accept a new Equivalence Principle, such as that?
To answer, I would ask, did Einstein and Newton, really had perfect/absolute/clear justification for theirs?