I don't understand this part. Can you give some concrete examples? In my experience, Google Gson and Jackson FasterXML can solve 99.9% of the Java Generic issues that I might have around de/ser.
I could, or you could use google.
Neither of those tools can solve any issue caused by type erasure.
Just to give some examples, the instanceof operator does not work with generic types, it's not possible to instantiate a generic type (can't do a new T()), can't overload methods that differ only in generic parameter type (so List<String> vs List<Integer>) and so on. Some limitations can be worked around with sending around explicit type info (like also sending the Class<T> when using T), reflection etc., but it's cumbersome, and not everything can be solved that way.
