With the PS4 launch in mid April a couple new servers were created.
The NA one is Jenova.
It is well populated and full of players still leveling up and learning the game.

I actually created a character on this server after I had hit 50 on a older, less populated, server.
Even though it probably cost me 150+ hours I'm glad I restarted.
There are a lot of console players on it though so if you are a PC you are a minority.