Let's just keep in mind that the entire reason languages with immutable data are trending is because we already have all those languages with mutable data to use where they are fit.
A new language today shouldn't really implement Python metaprogramming, because Python already does that.
Yes, and I think the reason why Nim got so much attention was because it filled the niche of metaprogramming in a statically-typed, AOT language, which is probably the last frontier of mutability and metaprogramming. It's probably the last major new language with metaprogramming front and center we'll see for a very long time.
Honestly, I don't think I'll ever create my own general-purpose language precisely _because_ I already know languages that are perfectly tailored to my use. If I start thinking of "what would my dream language look like", I start mentally re-creating Python. And sometimes, I might be in a different mood, and I'll think "wait, I'll make a statically-typed, AOT version of Python that I can use as a systems programming language instead of C/C++", and I end up mentally re-creating Nim, even to the point of going "well, I'll borrow the static typing part from Modula-3 because Modula-3 is cool and Python has a lot of Modula-3 in it already...", which is basically what Nim did.
A new language today shouldn't really implement Python metaprogramming, because Python already does that.