I get that you're referring to the current job market for most Silicon Valley programmers, and are well aware and mentioned more theoretical CS stuff, so the following rant is not directed at you, but at the ignorant buffoons one sometimes encounters in this space:
I find this notion so cute that programming is front-end or back-end, or maybe even both, i.e. full-stack. Reminds me of the scene in the Blues Brothers, where the eponymous heroes enter a bar for a gig and ask the proprietor what kind of music they play there, and he cheerfully answers: "Oh, we have both! Country and Western!"
There was actually (important) programming prior to the WWW, even prior to the internet. A lot of programming solves important problems, particularly in the business world, but has nothing to do with the interwebs.
Of the magisterial 5 volumes (4000+ pages) of Knuth's The Art of [wait for it...:] Computer Programming, estimated to be completed by 2025, I believe approximately 0 are concerned with web frameworks.