Theoretically it's not necessary, but given real-life constraints, there are most definitely times when null is more appropriate than e.g. Java's Optional.
Then we agree :). From a correctness perspective, nulls are awful.
My point was not specifically aimed at typed nulls and compiler optimization, it was that there will always be practical constraints that force us to compromise static guarantees in order to get things done in a reasonable amount of time. As software engineers, our problems are first practical before they are theoretical.
No. Java messing things up as usual, doesn't have any broader impact on the usefulness of the concept.
Error handling with null is wrong and broken, regardless of whether the null is "typed" or not.
null might have some very limited other uses, but they will never compete with those structures designed for error handling, because they do something fundamentally different.