You are not wrong. Eg the original Maxwell equation is so ugly (I think 20 of them) but the ones that are taught nowadays looks so elegant. The language is imp

You are not wrong. Eg the original Maxwell equation is so ugly (I think 20 of them) but the ones that are taught nowadays looks so elegant. The language is important. The more you “understand” something, the simpler it is (over simplification here.) eg I would not consider the Einstein equation expanded out to be natural after understanding it. (Well Maxwell’s equation can be summarized in 1 single elegant equation as well.) But the reason I’d consider that optics formula to be monstrous is that no matter how you group it into smaller pieces (ie refactoring it), there’s no way to hide the fact that it is not elegant at all. There’s no “understanding” there, it is just so happen the exact solution looks like that. To put it that way then, often fundamental “master equation” are simple in some ways, but exact solutions to some particular manifestation of that master equation is often quite ugly and monstrous. In that sense then rather than quoting Einstein equation I’d quote its solution eg one with mass and spin and electric charge. P.S. the solution of quartic equation is also a good example of this category