Fire got a nerf but it's far from useless now. Their new skills are very good.

The new mystery gives you pocket root of warrior for one turn and is an amazing way to stay strong against strong round 1 teams, or even cursed hidan teams.

The new standard trumps everything, since it hits everybody, relatively hard, and can even cause ignite.

Chases are chases.

The 1st new passive is essentially Lightning Main's Anbu Tactics, except for Ninjutsu. That alone is good stuff.

The 2nd new passive is essentially Warrior's Killing Intent for fire mains.

They've given discount versions of everything that made Lightning Main good, and kept the important passives (like the Oboro Clone) the same. The only really sad part of the nerf is the Genjutsu Mirror damage boost and the Dragon Fire mystery in general.
Imo, 2.0 opens up a lot of options for fire mains. You'll just have to adapt and play slightly differently to how you used to.