Your old gear is not unusable... however the armor stat-rolls will be out-of-date compared to how the new system works. No more hoping to get certain spikes on certain stats. New armor will have pre-determined rolls based on its archetype. There are 6 different archetypes, each focusing on 2 major stats, with the 3rd being random. Dont be surprised when you get new gear that has actual zero's in certain stats. This is a good thing now lol Example: for Assassin Cowl or Ahamkara Grasps, I'd want a "Brawler" archetype (big melee spike) instead of a "Grenadier" archetype (big grenade spike). I wouldnt invest too much in leveling-up your old gear, as you'll probably have to migrate to the new gear for the best perks & rolls. When EoF launched, we all got 20 free "Exotic Requisition Orders" to use at Ada-1... I would check your inventory for these, as they will allow you to claim 20 pieces of exotic armor by selecting exactly which archetype you want for each piece. (Like a "Paragon" Celestial Nighthawk, "Gunner" Lucky Pants, etc).