I see lots of discussion about the solution / what used to be done, but I want to point out why unofficial servers stopped being easy/standard/possible to run.

The first time big money entered esports was on private Starcraft LAN tournaments. Blizzard sued to get a cut of the proceeds, but because the privately-owned software (game and server) was running on privately-owned hardware, the courts ruled that Blizzard got no money.

AAA companies learned from this that allowing the playerbase to run their own servers meant losing out on money, so most AAA multiplayer games with even a small chance of ending up as esports make it so they can only connect to servers operated by themselves, longevity of the game be damned. If they weren’t so desparate for every scrap of cash they could possibly generate from the game, I would bet most multiplayer game would still let you run your own servers, like they used to.