First plot hole not all the players are from 1.0 the 1.0 players do not ride into the city in a chocobo carriage. We appear in the same area that derplander does in the movie that plays if you allow ARR to idle at the stay screen. Secondly, the new 2.0 non legacy plagues become the warrior of light after saving thancred (is more of a title than anything else)
Next you can still combat the primals even though the blessing was sealed due to the Echo which you still have that didn't get sealed. Which is shown in heavensward even worth all the crystals sealed.

Even to point out during the ifrit fight he tries to temper us but due to the Echo we can not be. The only time the blessing of light shielded us was during the fight against lahabrea and hydalen said it was out sword and shield. Basically we were tempered by hydalen before bit her tempering did not make us a mindless mess as the primals do for she still allows free will to some degree