Wow for example has the blizzard sponsored servers which you pay subscription for.

There are numerous community built private servers offering different versions of the game, some original & some modded, which offer a different experience and are typically free.

These servers are gaining in popularity as blizzard is incompetent in actually delivering a game/community that people like and want to play on.

Blizzard is definitely working with twitch/YouTube to remove all content from said private servers. Content creators can’t stream these private servers on centralized streaming platforms without risk of ban.

Here’s an example of a private server.

https://x.com/turtlewowteam/status/1811325435562672291?s=46&t=-NV56P9nSz0w8otFoURH8g