They've made it that way on purpose. There's a matchmaking formula that populates games with a large number of bots which allow for games to not be super aggro and allow for the games to last longer, letting events take place. The previous formula allowed for too many human players to bunch up and kill each other quickly before even phase 4, defeating the purpose of boss fights and mob hunts. They've stated before they didn't want the game to be too competitive or fast paced, even if it is a battle royale. Since they clearly want to emphasize their events and shit.
Hence why they actually make games not be 2/3rds or even half full of human players.
And here's season 3's trailer. The topside Midgar map is massive.