You do pay "up front" for Fortnite. For every season. It's constantly being updated and getting new content. You can continue playing for free with your old

You do pay "up front" for Fortnite. For every season. It's constantly being updated and getting new content. You can continue playing for free with your old skins and enjoy the game. You don't need to pay more. But you can also choose to get the new stuff, and you know what it'll be before you pay. In a world where toys in cereal boxes are considered "exploitative", I'm not going to argue that live service games aren't. But there's a world of difference between what Fortnite does and what Genshin Impact does.