>None of those things seem particularly modern to me. Does swift actually have any concepts that weren't already implemented in other languages by say, 1980?

Modern for mainstream languages. Non-mainstream languages are irrelevant to the discussion, since nobody cares about theme except niche industries, hobbyists and academics...

>but the flip side is - why not learn older, simpler, more mature languages that already have those concepts?

Because those languages are not tied to a $50 billion app industry or have major adoption and increased support.

It has options instead of null

To which the same argument applies.

Which languages before 1980 had an option/maybe type?

https://en.wikipedia.org/wiki/Tagged_union#1960s (and so on in the rest of the article; you could make the argument that being able to express a sum type and using option/result pervasively are different things; I don't know much about early ML but it was from '73...)

No, a sum type is the essence.

TIL that ML is ooold.

ML has roots that go back a long ways, but it wasn't developed as a general-purpose programming language (for use outside theorem provers) until the '80s, and I'd consider it properly "released" to the general public as something intended for real use only in the 1990s, with the publication of the Standard ML definition (1990) the release of OCaml (1996).

Protocol extensions.