I guess I don't see how generics would help you reduce the number of insert/update functions. The basic problem of an ORM is to map struct fields to columns; I don't see how generics would help you here. Can you write the generic pseudocode you want to write?
I would need one for each and every struct(table).
These days there is a tool that can generate all those struct methods: https://github.com/vattle/sqlboiler
So from the ORM perspective we (as the community) have worked around it.