elemental affinity is a missed opportunity. you should be able to put any mod in your armor regardless of affinity, but, if you do happen to align your affinity you should get boosts to your grenade and melee regen and maybe your super does some other effects that are special to each affinity. ldk, I saw the writing on the wall with this and it's the reason I didn't buy shadowkeep. bungie be struggling as of late to come up with anything truely new and innovative to the destiny universe.