I shall attempt a physics analogy to say they can both be true at the same time.
Inspired partly by this.
Gravity. In the equations of general relativity, we have 4th order tensors terms, so although the equation looks like one, in actuality, it contains 10 equations, coupled with each other in a non-linear fashion. So, although the underlying concept is simple: spacetime tells mass-energy how to move, mass-energy tells spacetime how to curve, the resulting thing is complicated. It’s not easy to find an exact solution to general relativity. If you can find one, it’s worth publishing and making a phd out of it. Even most space related missions, it’s not common to use general relativity, and we resort to the simpler newtonian gravity to ease calculations. Yet, the effects of general relativity cannot be ignored. GPS needs the correction of gravitational time dilation or else the errors adds up so fast, it becomes useless.
Even in newtonian gravity, each massive object attracts one another proportional to each of their mass and inversely proportional to the square of their distance, the underlying law is simple, but even 3 body problem is unsolvable analytically.
So too, kamma has a simple underlying concept of do good get good, do bad, get bad. The mechanism by which it plays out becomes complicated as we have to account for cause+conditions then results can happen, and many lifetimes, the strength of the kammas, the virtue of the person, the relative abundance of good vs bad kamma collected etc.
So it’s not true that with just high school physics, or even learning general relativity in University, one can join in the space missions and do the calculations straight away, there’s a lot of technical manuals to master, the experiences, how to work with computers to calculate what etc…
So although gravity is complicated, one would still not simply walk off tall buildings, or drop a brick onto one’s foot. It’s also that simple. Things fall. So it’s good to learn about it, both the complicated and simple formulation. Same too with kamma.