Heavily generalizing of course, but:

Only in so far as the user actually _can_ make those changes, if deemed necessary or elegant using macro facilities. Once something has proven itself good enough to be part of the language standard, there is nothing limiting language maintainers/creators to take it into the standard and ship with next release. So it is strictly more flexible in that way and users do not have to wait on commitees.

Python does too, to a limited extent. A good example is type annotations. You don't _have_ to use type annotations, but you can enforce it in your project by writing a typechecker or a preprocessor; and there's a subset of python that can be compiled statically.

And the Clojure example imho is a bit of a red herring, because while it allows a lot of flexibility (reader macros in Clojure are very powerful), they don't encourage ecosystem divergence, since Clojure can use JVM/Java for "Batteries" and most standard libraries. Cljs is more similar in that way, because it carries much of javascript's divergence with it.