[TheAsprngHacker]

You can have recursion right from Beginning Student Language (which lets you define top-level functions and call them recursively). Structural is taught early, together with lists. Structural recursion is explained together with recursive data: To unpack the data (any data, not just recursive), unpack the inner members, and therefore the structure of the program follows the structure of the data.

As someone who is taking the accelerated version of this course right now, but had prior functional programming experience, I did feel limited at first. Some other people responded negatively to the student languages because they weren't "mainstream."

As for the expressive power of languages, as a matter of fact, Felleisen wrote a paper that rigorously defines this idea. Here is a talk by Shriram Krishnamurthi that discusses it: https://pwlconf.org/2019/shriram-krishnamurthi/ It turns out that local transformations (macros) do not add expressive power. A language feature adds expressive power if you can find two programs that are observationally equivalent in the base language, but not the extended language.