Nope. All Un-set cards were legal only until January 15th.
Modern is in the best place it could possibly be in right now. 30 different decks all had positive scores at the most recent Modern Pro-Tour. It's the healthiest it's been in recent times.
Ehh..? Modern power levels have risen with the increase of card choices new sets have given it. He's a powerful card, but not as broken as he used to be, outside of a vacuum.
They really are only unbanning him so they can sell reprints in Masters 25.