Second, modern 20th century physics education (courses, textbooks) suffered sustained corruption of methodology by scientific authorities, where the quest for understanding was renounced in favor of "modelling" and "prediction" (e.g. authors of orthodox quantum theory and their less bright pupils perpetuating that attitude) and later by institutionalized system of university research which propels tweaking and applying old ideas to detriment of trying new ones or questioning past ideas that are too ingrained.
This leads to a large portion of theoretical physics publications being more and more about complex calculations where most applicators do not even try to understand "what is going on", they just assume the same quantum methodology with some tweaks (i.e. different configuration spaces, more dimensions, different Lagrangians, new fields that fix problems of the previous ones, tricks with removing some ugly series terms etc).
Sometimes these tweaks get fancy names (superstrings, loops, dark matter) but they are really an additional concept that needs to be put in to save the edifice from those radicals who would like to try actually new and incompatible ideas.
When you study 20th century physics yourself from original sources, you'll find the stuff taught currently actually has highly varying degree of credibility. Some stuff is rock solid, such as relativity, molecular theory and chemistry, nuclear physics and solid state theory, and some stuff is ... well, more unfinished and less credible - such as standard model, force unification, quantum gravity, dark matter, etc.).
If you want to get some solid ground on which to build intuition, start with the rock-solid physics as known till 1905, then after that makes sense, learn about its problems (explanation of emission spectra, inconsistency of EM theory with Newtonian mechanics), then after that take a deep breath and read original papers on quantum theory and particle/nuclear physics.
This will take years to understand. The later theoretical stuff around Standard Model details (lepton generations, stability of particles, unification of gravity and QFT) is a decades old project that nobody knows how to finish. It is stuck for now, and has little relevance for understanding those previous things.