I wouldn't say that they are pointless, even if you are restricting party members to specific weapons & armor types. Because if you have multiple potential party members, it incentivizes the player to use certain characters during certain times. Which gives your player another reason to have greater familiarity with a larger roster of characters, rather than only using their favorites.
Personally I like using them, because with my current project I allow my player to create their main character, as well chose the class, subclass, & skill loadout of each character. & the characters skills grow more powerful overtime, based upon which skills they use. So having different weapons do different forms of damage actually works rather well, because the combination of a limited loadout, coupled with extensive choices allows them to craft a party that is uniquely "Their Party".
I would say that greater variety only becomes pointless, when it becomes redundant, i.e. it doesn't have any effect on gameplay. For example have a frost element & a fire element have rather obvious implications. However having a fire, plasma, & heat element are quite a bit more difficult to have meaningful game mechanic differences between.