I've been reading that people are rethinking Grand Unification, and that perhaps gravity is not compatible (or unifiable) with the other three forces. And no theory of quantum gravity appears to work.

My own view, which respects well-confirmed science, leans toward a clear distinction between the relativistic macroscopic and quantum 'microscopic' realms.

As I get it, General Relativity brilliantly articulates the spacetime orientation of human perception. It's concise formulations describe relations among observable phenomena ranging in scale from atomic to cosmic.

Wikipedia — GR: en.wikipedia.org - General relativity

General relativity ... is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present.

On the other hand, the Standard Model of particle physics addresses fundamental phenomena originating at subatomic scale. Most striking for me are the hypothesized quarks that underlie materiality. Atomic nuclei are comprised of observable protons and neutrons, each of which consists of three quarks. Quarks serve as the interface between seemingly permanent matter and nondescript infinite potential. It's notable that while protons may persist for billions of earth years, their component evanescent quarks evade detection, at least to-date, other than by their effects.

Wikipedia — Standard Model: en.wikipedia.org - Standard Model

The Standard Model of particle physics is the theory describing three of the four known fundamental forces (electromagnetic, weak and strong interactions – excluding gravity) in the universe and classifying all known elementary particles.

I'm no physicist, and struggle to integrate their complex findings. Thankfully they widely banter among themselves. Acknowledging all that, my current takeaway is that the evolving world of human experience is presently most effectively described by relativity, and its emergence into existence is best described by quantum theory. They don't need to thoroughly integrate, although it would be stupendous if they did.

As I see it, the bottom line is that everything is now,
suggesting a block universe comprised of all evolving within it,
evoking spacetime in the human venue.

Fundamental singularity boundlessly complexifies,
ubiquitously hosting whatever's happening here now.

Cognition is emergent within experience.
Absent emergence, there's no experience, much less cognition.

As an aside, my writing is an exercise in clarifying my own thinking rather than an argument for its validity, shared in the hope of advancing the understanding and eliciting the responses of others.

Tom