I dont really understand what macros get you when llms exist since a llm doesnt really need to create dsls to get work done

> To my knowledge Common Lisp is the only mainstream language that does all of this.

Sounds like someone who has never used C# and Visual Studio? Even JavaScript is capable of doing this, honestly JavaScript might be the one language with the richest developer tooling of all time (possibly?), sad to say because there's nicer to work with languages out there.

Maybe you could take CL as a foundation, introduce modern features and uniformity to the language, remove some of the insane complexity, tame the unhygienic macros, and come up with a pretty good language. Since about 7392 different flavors of scheme have tried to do this and mostly failed, I think this is very unlikely.