What is the Difference between Macroscopic and Microscopic Physics?

Multiscale modeling with simple ordered microscale (atom) and ordered macroscale (car) connected by complex intermediate scales.

The standard view is that classical physics is useful to describe the macroscopic world, like the flow of air around an airplane or the formation of a galaxy,  while the microscopic world of atoms and molecules requires a fundamentally different form of physics named quantum mechanics.

The standard view is thus that the world is divided into a macroscopic world and a microscopic world supposedly governed by different physics. The standard view is that we as human beings with experience from the macroscopic world cannot fathom the microscopic world because it is so fundamentally different from the macroscopic world.

But is it really reasonable from a scientific point of view to divide the world this way? What is the dividing line? How does the microscopic world interact with the macroscopic world?
Is it possible to tell if a mathematical model in its typical form of a differential equation describes microscopic or macroscopic physics?

None of these questions has a good answer and it is then natural to seek the origin of the idea that microscopics is so different from macroscopics. The standard wisdom says that microscopics is described by quantum mechanics and macroscopics by classical mechanics and quantum mechanics is fundamentally different from classical mechanics and therefore macroscopics is fundamentally different from microscopics.

The standard wisdom according to the Copenhagen interpretation of quantum mechanics is that the microscopic world is a strange world without causality and predictability functioning like a microscopic game of roulette. This strange idea comes from the insistence to describe microscopics by a multi-dimensional linear Schrödinger equation, which because of its many dimensions can only be given a probabilistic interpretation and not a physical realistic interpretation.

The multi-d linear Schrödinger equation is an ad hoc model which is not derived from basic principles and thus is accepted as a true mystery beyond comprehension of human minds and as such necessarily a correct description of microscopics.

But suppose, we do not take the incomprehensible (and uncomputable) linear multi-d Schrödinger equation as description of microscopics, because this lacks rationale. Suppose we seek instead a description in the form of field equations in three space dimensions plus time, in the form of Hartree models as non-linear coupled systems of one-particle Schrödinger equations, which have the same principal form as macroscopic continuum models.

Then there will be no fundamental difference between microscopics and macroscopics and all the problems arising from postulating such a difference will disappear. This must be a good case for Ockham's razor.

Note that claiming that microscopics functions like a game of roulette is contradictory, because a game of roulette requires microscopics, which leads to an infinite regression of microscopics upon microscopics. When I present this argument, which makes perfect sense to a classical physicist, in a discussion with a modern physicist, I get no response as if this argument is beyond what is allowed in modern physics. Is this reasonable?