I have been both a teaching fellow & a post-doc and appreciate the point!
But your example was either a “small point” or it was “core” principles, as you used in your physics analogy. In survey courses there will always be many, many small points that are dropped (actually, in any teaching, really, even when the teacher is an expert!). I am a huge fan of the Core, and fully on-board with the merits of an education that at the very least flags to students that in Literature, History, Art, etc there is always context, and understanding that context is an important part of understanding the thing itself.
But: you don’t have to know each of the specific flower symbols to know that in Art there is an extensive lexicon of flowers, and that if you see a flower in (say) a Renaissance or Victorian painting it is almost certainly there for a specific reason - and you can look it up if you want to know more ("go look it up’ being the mantra of my childhood).
When I compare the Lit options available at the schools and universities that I know best and compare them to the ones when I was coming through, I can see arcs as a ‘new’ field opens, peaks, and then settles down into some degree of normalcy. Imo the Collegekids got the best of what I got, plus some great new things, and some not-great new things. And, some of the old stuff they got has improved since my time (eg, they got Seamus Heaney Beowulf!). I think I am just more sanguine than many of the posts in this thread that the sky is not falling, that the Good Ship Literature has weathered many fads and fashions and will keep plowing ahead- and that while making room for a bigger crew may make things rowdier and messier- especially at first, when the Old Salts adjust to the newcomers- overall it yields more hands on deck.