The only thing I really missed, has been adopted during the latest years, pattern matching.
Languages are not used in isolation, great IDE experience, and having mature libraries for every use I can think of, is more valuable than grammar and semantics.
Also a reason why I would rather do FP in C++23 than Haskell, even with all the warts and paper cuts it entails, ecosystem.
If only the tooling was at the same level as C# and Java.
Additionally, they add friction to a development stack, now everyone needs to be confortable with two language stacks, and most of the time it isn't really worth it.
Languages are not used in isolation, great IDE experience, and having mature libraries for every use I can think of, is more valuable than grammar and semantics.
Also a reason why I would rather do FP in C++23 than Haskell, even with all the warts and paper cuts it entails, ecosystem.