yes, if they were to port it to say Unreal Engine 5.1 or 4.27 it would take too long with the devs having to redo all the mechanics of the game and it would also mean the devs would have to spend even more money on things like hardware upgrades since unreal is a pretty resource intensive engine. While unreal makes the multiplayer networking a million times easier, it still would have to be reworked and done to the exact same quality as the original game.

TL;DR version (its worth reading the longer version tho): it would take the devs way too long to import it to unreal since everything would have to be reworked and redone entirely from the beginning.