Learning Prolog for "mind expansion" feels weird in 2021.

As a language (at least SWI-Prolog), it's missing some niceties that I took for granted: e.g., a function's output is always to a C-style output variable, all "context" variables must be passed around in recursive calls, etc.

There are several well-regarded books on Prolog that also feel quite antiquated in their concerns: authors taking pains to build elaborate conventions around function naming and argument ordering, etc.

Aside from its unusual features, Prolog really feels like a language from the early 90s, with a small, static standard library you might memorize, and authors offering "helpful tips" around functions with slightly different names in "commercial systems."