I think people are mostly just upset because it changes the metagame considerably, and any time anything changes the metagame people freak out (Fairy-type, MegaPokemon, Steel losing Ghost/Dark resistance, etc)
The main argument i keep hearing is that moves that aren't electric typed that cause paralysis (like Body Slam) should still effect it.
Well we have water moves that burn but doesn't effect fire types. We have grass and bug moves that can poison but doesn't effect poison types.
All of those none Fire burning attacks involve heat/fire even though they're not technically Fire type. Example: Scald shoots super hot water. If dual type attacks were a thing, Scald would be Water/Fire. Same is true of freeze and poison, they all clearly involve cold or something. Also, there are no Grass moves that cause poison, although that could still make sense.
However, there are paralysis causing moves that have absolutely nothing to do with electricity.