"Turning off nostalgia goggles, there really is nothing much to the game without its online mode."
Um, this is a false statement. The Gamecube version has 4 player splitscreen. Other than some specific events and a few quests, the entirety of PSO 1-3 are playable offline on Gamecube. The game is fun due to the loot grind still to this day, and that loot grind is still possible to do today on a Gamecube, and I still do it, exclusively offline. I don't play on private servers.