Nukes are only fun when they've got an atmosphere to send a shockwave through. In zero-atmo, all they do is act like a regular dirty bomb, and most spaceships are expected (and designed) to handle far stronger radiation.

A beaming block is only so strong. Given time, it can be worked past. Especially when the source tech is primitive. (wraith had ancient-level tech, whereas most others have goa'uld-level)