Newton's law of gravitation and Einstein's general relativity (GR) are empirical laws of gravitation that are strong on description and prediction but lack deterministic and/or causal rigor, which makes both of them incompatible with the fundamental laws of physical reality.
Newton's action-at-a-distance is acausal because it does not explain how gravitational force can be projected over infinite space and time without propagating from a source at a finite speed, and it violates the law of conservation of energy because it cannot account for the energy expended by matter over infinite space and time in doing work on other matter without losing mass or energy.
Einstein's concept of a curved space-time that implies "trust me, the curvature is just there", provides no credible physical explanation for the curvature and is therefore non-deterministic, while it too violates the law of conservation of energy for the same reason as Newton's law.
How can we ignore the implications that in both Newton’s law and Einstein’s GR, matter-on-matter attraction leads to an increase of collective kinetic energy without loss of mass by the mutually gravitating bodies? Where is the “bonus” energy coming from? It is tempting to claim that a certain mysterious gravitational potential energy is converted into kinetic energy, but that is not a valid explanation without causally determining the physical mechanism/process that creates the potential energy in the first place. In short, even Minkowski's mathematical wizardry was insufficient to elevate Einstein's creatively brilliant GR concept into the realms of "hard physical law", but it did impress a lot of mathematical physicists who fell in love with the intricate mathematics so much so that they inadvertently ignored the physical laws of nature that were blatantly violated.
A true law of gravitation will not rely on the empirical non-deterministic dogma of Newton's action-at-a-distance or GR's "let there be curvature by fiat", even if both are experimentally verified a zillion times, until the inevitable anomalies start creeping up from left field, as they did in the case of the Pioneer anomalies and the flyby anomalies, to mention a few; don't get me wrong, Newton was a sage of natural philosophy but his gravitational theory was perhaps the best he could have done at his time. Einstein was no doubt a genius at what he accomplished, but geniuses are human and have their limitation also.
Anyway, regarding the ongoing quest for the true law of gravitation, the prospects of relying on quantum physics/quantum gravity are no more promising than the prospects of surrendering to the probabilistic empiricism of implied ignorance that we call probability theory; sometimes we do not have a choice. Is it not perplexing that otherwise respectable physicists who proudly proclaim that "anyone who thinks he understands quantum mechanics does not" continue to preach its teachings from a position of dogmatic dominance.
So, I ask again, can Newton's law of gravitation and Einstein's GR be considered true and complete laws of gravitation? If not, what will a true law of gravitation look like? Where should one be searching for a true theory of gravitation?