I might have said that for myself (I even wrote a Masters thesis about extending Prolog and efficiently implementing it), but Prolog forced me to learn a new paradigm of programming and that has been useful (Lisp, Smalltalk, APL, Erlang also taught me new paradigms). And I learned SQL by asking a colleague at IBM's Almaden Research how to translate my 5-line Prolog queries into SQL and he'd respond with a page of SQL.
Nothing you spent time on is ultimately wasted time. Like you, Prolog taught me a lot, maybe nothing that was immediately useful, but a mode of thought and a mode of understanding.
"The time spent on Prolog was mostly wasted".
I might have said that for myself (I even wrote a Masters thesis about extending Prolog and efficiently implementing it), but Prolog forced me to learn a new paradigm of programming and that has been useful (Lisp, Smalltalk, APL, Erlang also taught me new paradigms). And I learned SQL by asking a colleague at IBM's Almaden Research how to translate my 5-line Prolog queries into SQL and he'd respond with a page of SQL.
Now that I'm retired, Prolog is an amusing hobby (https://github.com/SWI-Prolog).
BTW, like you, I also got lucky (a Google recruiter found me in 2004 - and I failed the interview - but I got a second chance a few years later).
Nothing you spent time on is ultimately wasted time. Like you, Prolog taught me a lot, maybe nothing that was immediately useful, but a mode of thought and a mode of understanding.
Like your writing, Jos!