Because the more desirable fix was requiring explicit annotation for "new" virtual functions, and make silent hiding an error. Instead, we have situation where you have to write "override" everywhere to get the desired sane behaviour.

I agree that explicit annotation for overrides is desirable, but disagree that it alleviates the need for `override`. The fact that a method is introduced for the purpose of overriding is IMO important enough to justify an explicit annotation regardless, much like C# does it with `new` and `override`.

It's also not clear to me what this has to do with ODR, ADL etc. That is to say, it's obviously a problem with a historical design decision (implicit overrides) that now has to be kept for backwards compatibility reasons, making it impossible to require a `new` annotation above and beyond opt-in compiler warnings. But that particular problem is not a uniquely C++ one, seeing how implicit overrides are actually more common than explicit ones in mainstream OOP languages, largely because they have all inherited this choice from either Simula (as C++ did) or Smalltalk. C# is more of an exception in that regard.