True, but in a language that's designed to quickly make other languages, the rigidity can be controlled by the system architects.

An example of a current language with this philosophy is actually Typescript. The gradual typing means that you, as a module designer, can choose to make rigid exactly what you wish (and choose how much rigidity you require). If the consumer of that module also uses Typescript, your rigidity requirements will be respected.

The reason we don't think of programming languages as being per-project, per-module, per-domain, etc, but rather as large global things is because we don't currently have a clue how to do that (and if we did, we don't have a clue how to make the tooling work). If and when we do, these types of conversations will seem quaint.

One can hope, anyway...