Comment by mirashii

What language that is actually used 40 years after release isn't undergoing big, fundamental changes?

Java? Nope, you're getting a fundamental change in Valhalla C++? Nope, new language edition every few years with fundamental changes C? C23 has a number of fairly fundamental changes, expect more in the next language revision

I think your sense of causality is backwards here. These languages are getting fundamental changes because they're being widely used. That is what motivates and drives the change. Languages with no users don't need to change.