Let me open the shutter and give you a bright shining vista. A belvedere. Spacetime is curved, and curvature can be quantified, by tensors. Ricci tensors, Einstein tensors, metric tensors, Riemann tensors, mass-energy tensors, or whatever tensors. The are collections, tuples of tuples, of number concerning positions and lengths, time and durations, a lot of (partial, directional, single or multiple) derivatives thereof, and a dual flat, Minkowskian, (co)tangent space is introduced locally, to facilitate calculations.
Then on this space particles fields couple with an eternal and all-pervading field of virtual particles by means of which they reach out to other particles (Haag's theorem says virtual particles are math constructs, but a similar argument can be constructed for real particles). If they get no interaction, they will get lost in space hopelessly.
These particles and their couplings to the virtual field (by charges, which are considered the generators of the force mediating fields, giving the misleading image of force being the result of particle exchange, which doesn't happen), these particles and their couplings to the to the virtual fields between them (the intermediary fields, like the field of intermediary vector bosons in the weak interaction, or the photons between charged particles), are described by quantum fields, as you certainly know.
The coupling to the virtual fields, and the couplings of these fields to other virtual fields, is represented by Feynman diagrams. There are an infinity of them, corresponding to increasing numbers of interactions with and of the virtual "glue". The charge of particles determines the glue strength, i.e. the coupling strength. If this coupling is strong, like is the case for the color force in the strong nuclear force holding quarks together, the
Feynman diagrams contribute more and more instead of less and less, as is the case in the electrons interacting. And because quarks can never be asymptotically free, the perturbation approach can't be used to describe quark interacting with other quarks, as the perturbation approach assumes the particles to be free before and after the interaction. If the quarks are close to each other, the effective coupling is small, letting them run fairly free while forming a proton, neutron, pion, or more generally, hadrons and mesons.
To describe the motion of these quarks the approach with Feynman diagrams (the perturbative approach) won't work. There are other non-perturbative approaches like those lattice calculations assuming a discrete structure of spacetime. Supercomputers are used to do calculations in this color charged realm.
So perturbative QFT is applicable in a very limited domain, and extending it to curved spacetime complicates the the app. QFT in curved spacetime was used by Hawking in his description of the eponymous radiation. But the calculation is approximate. It's rather well understood, but there is no connection involved between the information inside and the radiation. This connection has been established recently (by entanglement), but there is no consensus.
So the math never describes exactly and at most approximations can be made. Which simply means no exact structures exist. Which means they don't exist at all.