Kotlin has become a pretty big and complex language on its own so I'm not sure this is a good counterexample.

The fundamental issue is that fixing Scala 2 warts warranted an entirely new compiler, TASTy, revamped macros... There was no way around most of the migration pains that we've witnessed. And at least the standard library got frozen for 6+ years.

However I agree that the syntax is a textbook case of trying to fix what ain't broke. Scala 3's syntax improvements should have stuck to the new given/using keywords, quiet if/then/else, and no more overloaded underscore abuse.