Lightning Energy allows electric type Pokmon to hit for 20 more damage and considering that we will most likely head into a format where Mega Evolutions are the norm, this damage boost might be the difference from getting a big KO or not
ETB Triggers Phoenixes tend to die and hit the battlefield multiple times per game
However, with a card this pretty and rare, it is unlikely to see much time in play
Looking beyond cards that directly reference +1/+1 counters, these decks can and should make ample use of cards that care about modified creatures
Brago, King Eternal and Aminatou, the Fateshifter dont have to worry about mass blinking and only getting one Illusion
If I ever run this card, my goal would be to cast a bunch of instants/sorceries, make a bunch of Otters, and then move to combat with Shared Animosity and just demolish my opponents with my cuteness