How i feel about competitive players and casual players in EDH: The competitive are german tourists, the casual are italian tourists, both in a italian beach. The italians asking themselves "why are the germans here?" make a legitimate question, the answer is because the beach is beautiful, no matter the country you came from. The italians wanting to ban the germans are dumb, because if the germans pay for their stay and follow the rules like everyone else, they have the right to be in the beach. Hovewer, if the germans started to ask themselves "why are the italians here?"... they would be dumb as hell.
"Phoenix with set mechanic" is getting somewhat tiresome, but I guess rising with the dawn is pretty cool flavor. Rising at nightfall as a beacon of light against the coming night works too.
Card seems pretty good too. For a deck that can operate at instant speed, taking your turn off to have it turn from day to night to get back the phoenix (untapped!) at the beginning of their turn seems nice.
It seems like the only downside to this will be getting the day/night cycle started. You don't actually want to cast this to be the start of the mechanic - you want to rummage it away and get it back on the cheap. Most of the day/night enablers are 3 cc or more and that doesn't bode well for the mechanic to be hugely relevant even in standard.