OpenVMS native IO code, in C, can certainly get rather hairy, from what I’ve seen. For example, the OpenVMS port of SQLite: https://github.com/endlesssoftware/sqlite3/blob/8004eeafeec9...

When you speak of “more ‘native’” languages, what do you mean? BLISS? MACRO? Pascal/BASIC/COBOL/FORTRAN? How do they make code like that simpler?