Why are you using the symbol + to denote the unification of theories? That isn't how it's done.

Of course it's trickiest to integrate gravity, but NOT because gravity has a "generic quality". Electric fields are generic too. A proton in the Andromeda galaxy can, in principle, pull on an electron in our galaxy, both with electrostatic attraction and gravitational attraction. And, indeed, the electrostatic attraction is decillions of times stronger, and works on if not every particle, a very substantial fraction of them. Except that electrostatic interactions are signed, and the electric field induces movement of charges and currents and so on that effectively counteract that static charge, whereas gravity has a single sign and therefore no shielding.

The spacetime bit is trickier, but how tricky? That's not clear if we're not trying. Maybe there is a unification of theories that's possible, or maybe not, but how could we tell if we don't try? Indeed, it's not even clear experimentally that the unification of the strong interaction with the electroweak interaction has been successful--or that it's even all that important, because that fields become unified at incredibly high temperatures does not have many practical consequences for the temperatures we normally encounter in the universe (e.g. at the center of stars, or even during supernovae and mergers of black holes and neutron stars and the like).

Anyway, the problem is that you are simply asserting that gravity is different. But the forces are all different! Indeed, even electricity and magnetism are different from the perspective of a single reference frame.

For your large picture to explain something, it needs to actually have some substance to it. If you think gravity is a matter of relationships while other things are intrinsic properties you need to show it. The analogy to family is incredibly easy to understand. This is really immensely trivial. There is no problem understanding that. The problem comes when you ask: okay but what is the evidence?

I can imagine all sorts of things. Maybe forces are computations, but gravitation is the density of computations and not anything separate itself. Maybe "gravity" is three forces itself, mostly unified already, but not quite, and on universal scales the three forces explain conventional gravitational attraction, "dark matter" attraction, and "dark energy" expansion. Maybe panpsychism is correct and everything has a degree of "experience", and gravity is a result of a desire to have mutual experiences.

With a bit of creativity, you can come up with all sorts of things with superficial plausibility, but either no substance, or radically wrong predictions, or both. To even be interesting, you have to get past that into something with predictive value, more substance, something.

I'm not seeing that with your big picture. Sure, things could be different. Fine! No problem! Not a hard idea at all. It's not profound, at that level, it's easy. So easy that it's hardly even worth mentioning--everyone working in physics has similar types of cognitive manipulations all over the place, whether you want to understand spin glasses or reverse osmosis or whatever.

The question is: what are the consequences? What are the actual detailed nontrivial conclusions? Or what is the precise argument that the nature of gravity is fundamentally different exactly in the way that you say?