Einstein's text below suggests that a physics theory is either an empirical concoction or a construction "built up logically from a small number of fundamental assumptions, the so-called axioms":
Albert Einstein: "From a systematic theoretical point of view, we may imagine the process of evolution of an empirical science to be a continuous process of induction. Theories are evolved and are expressed in short compass as statements of a large number of individual observations in the form of empirical laws, from which the general laws can be ascertained by comparison. Regarded in this way, the development of a science bears some resemblance to the compilation of a classified catalogue. It is, as it were, a purely empirical enterprise. But this point of view by no means embraces the whole of the actual process ; for it slurs over the important part played by intuition and deductive thought in the development of an exact science. As soon as a science has emerged from its initial stages, theoretical advances are no longer achieved merely by a process of arrangement. Guided by empirical data, the investigator rather develops a system of thought which, in general, is built up logically from a small number of fundamental assumptions, the so-called axioms." https://www.marxists.org/reference/archive/einstein/works/1910s/relative/ap03.htm
In other words, equations in a physics theory are either guessed or (possibly guessed initially but then) deduced from "a small number of fundamental assumptions, the so-called axioms":
Richard Feynman: "Dirac discovered the correct laws for relativity quantum mechanics simply by guessing the equation. The method of guessing the equation seems to be a pretty effective way of guessing new laws." http://dillydust.com/The%20Character%20of%20Physical%20Law~tqw~_darksiderg.pdf
Except for special relativity which is an axiomatic construction, theories and models in today's fundamental physics are empirical concoctions.
If the theory is axiomatic, as is special relativity, then it can only be spoiled by a false axiom or an invalid argument (one in which the conclusion does not follow from the premises). If the theory is not axiomatic, that is, if the method is "guessing the equation" and not "deducing the equation from axioms", then the theory is already fatally spoiled by the mere fact that it is not axiomatic. Such theories are not even wrong.