Problem is with current editor you can make your own game out of other game, so Epic can’t just let editor out with current engine distribution model. There 2 solutions for this problem:
-Epic makes limited version of editor or let you construct one
-If engine unfriendly does not need to mean that your game needs to be unfriendly. You can make modding tool in the game, by making editor in game, implementing scripting language or at least external files which let you edit the game.
Even so… you don’t need to even care about it as modding community will always find a way to mod your game 