to fuse a general explanation for the mechanism of everything and science is a defeating purpose to the framework of science itself. for instance, logic and the inductive method, or scientific method are insufficient for good reliable scinece. there is no ultimate truth. as of history, we learn far more by attempting to falsify a hypothesis than trying to confirm it. falsification helps to uncover novel ideas, because confirmation produces little new insight.

coming up with a unified theory is simply just an estimation. to understand the universe is to understand strings. unfortunately, to understand strings is to observe higher up dimensions, which is improbable at given time and technology.

as OP has mentioned, the problem faced with this theory is the colliding thoughts of general relativity and quantum mechanics. the latter concretes its foundation of teaching with four universal forces, while the other says the higher the energy or the mass, the higher the force of gravity. so the smart scientists have come up with a new idea that dark energy is what responsible for the formation of gravity force by studying the way universe expands and so on. but to observe dark energy, or dark matter, is too physically improbable. and force it creates are then retained by photons which in turn expands the universe consistently.

so while waiting for the good people at CERN to come up with something, the universe is already an entirely different being. so basically, the theory of everything, well its just an approximation of the physical world of the past, if they do come up with one.