One can also look at, say, concurrency. A topic often seen as unimportant in the 90s, but ultimately taught at the lowest level, with mutexes, threads, semaphores and such. Those aren't going away, but how often is concurrent programming all about manually setting mutexes? We use higher order abstractions, but those change too. Many languages are encapsulating this in monads, whether people know their promise implementation is a monad or not. But that's not the only way, and the most popular way can change: Maybe languages in 10 years will be all about continuations and direct styles. Maybe it'll be something else. The fact that in the end, the same basic features from the 80s and 90s will exist at the bottom somewhere isn't that useful for most programmers.
And html generation... I was writing UIs before web apps were there. A lot of things that seemed fundamental went away when the browser was embraced. But will the browser live forever, or be superceded? I suspect that it will all get replaced, or be utter legacy, eventually. Will that eventually be 10 years? 30? It's very hard to say what will remain fundamental, and what will not.
Also, programming languages in 10 years from now will be pretty much the same languages we have today. There might be a newcomer or two, but it will be niche, as incumbents don't really change and only grow.
As a reminder, for people thinking that technologies change too fast, POSIX is still here and as relevant as ever.
Structured Analysis and System Specification, Tom DeMarco, 1978.
I've also heard good things about 7 programming languages in 7 weeks, as well as crafting interpreters.
The latter 2 I intend to pick up this year
Data structures, algorithms, algorithm analysis, various discrete math topics (set theory and number theory, a bit of graph theory, are usually included in a typical CS undergrad curriculum), models of concurrency, models of computing (lambda calculus, Turing machines), complexity classes, Chomsky hierarchy, type theory (some might consider this more advanced, varies by school and its lean towards practical or theoretical CS), systems of logic.
https://sarabander.github.io/sicp/
If you want to run these locally, I can set Chicken Scheme for you.