There was lots of discussion and debate around that time on topics such as static vs dynamic, clojure vs haskell, java vs scala, oop vs fp, js vs ts, new languages vs established languages, conferences devoted to FP ideas, etc...
I think it's probably obvious that devs, who have free time, use their attention to learn on whats trendy. (Rust probably took some wind out of the sails of haskell in terms of mindshare, for example).
I'm not sure what trendy is moving to these days, maybe AI, but do devs really program against large AI models, or just play around with chatgpt.
If not, what are they interested in with regards to tools that materially affect their career?
- What happened to interest in FP (measured in frequency of online discussion)?
- What happened to all the debate around languages?
- Is Rust still trendy in dev mindshare?
- Are these debates over/resolved?
But I think the steam on FP hype was already starting to run out for unrelated reasons.
The briefest account I can offer on "peak FP" from my (web developer) perspective is that
1) functional programming was already enjoying a moment of renewed interest and vitality due to the increasing ubiquity of multi-core,
2) React/Redux -- which ~solved[1] many problems with increasingly complex frontend web/mobile state management -- really started to become mainstream around 2016-2017,
3) Node/TypeScript was in the midst of an popularity / enterprise adoption explosion (in part due to #1) and only served to amplify the general enthusiasm around FP among JS-literate engineers (in part due to #2).
In the intervening years, the React paradigm more-or-less "won" and multi-core is taken for granted. A huge chunk of our industry has probably never known a time where FP wasn't celebrated. For that reason, it no longer seems to be answering any pressing problems, and naturally there are fewer articles being written about it.
[1] I expect this to be a point of consternation, since this is HN, but the point is that React was at least _perceived_ to have been an antidote to a variety of issues people faced with Angular, Backbone, plain old jQuery apps, etc. and the unifying theme of those issues was (rightly or wrongly) perceived as "OO / mutable state bad."
Yea, everyone else probably knows that. But maybe I'm tired, but it took me a while to parse that.
IMHO it would be more productive if you defined what definition of FP you are using, because it seems very broad.
As for what is trendy, I am afraid I cannot help there.
And when it comes to LLMs/AI a lot of the code used to train, run inference, and actually use in products is Python, C/C++, and maybe JavaScript. Not Haskell or Clojure or Lisp or anything like that.
Basically the FP discussions are old news.