RPG Maker XP was released in 2004, nearly 20 years ago, and yet the entire Pokemon fan game community uses it exclusively. Pokemon Essentials, by far the best framework for creating fan games, is written for it, and is still maintained to this day. It’s such a large complicated project, with a huge ecosystem of plugins and resources, that it’s impractical to migrate to the newer RPG Maker software that has been released since.
Drives me crazy when I see this kind of format for things like programming. Nothing like pausing the video and trying to see what their code says.