Sure, I get that, but without land for rivers to essentially mine salt from, the equation changes a lot. Underwater erosion is dramatically less destructive than above water erosion.

Earth’s oceans are in a steady state, where all the addition of salt by rivers is balanced by loss of salt in the ocean. If you removed all the rivers from the equation, Earth’s oceans would find a new balance at a point significantly less salty than they are currently. Though I have little idea if that would be something we consider freshwater, or just “less salty” saltwater.