I see exotic gear as the point where you choose how to "spec" your character, similarly to how you choose your talent tree in a typical MMO. Let's say you opt to roll with
Lucky Raspberry. With its arcbolt grenade and fusion rifle upgrades, you are essentially speccing yourself to be a shock damage hunter with a fusion rifles (optimally Plan C to go for a full shock build). A class needs to commit to a spec when choosing what exotics to wear. I find this system incredibly rewarding and a lot more flexible than locking you down with talent trees since you can always swap gear and subclasses between fights. These elemental speccing will be even more prevalent when more and more people start acquiring elemental damage main weapons.
In the future I totally see people looking for fireteams by saying "LFG lvl 30 void spec shotgun warlock" or "LFG lvl 29 fire spec handgun hunter."