Well, the falna system is literally like any rpg where you can earn EXP. So yes, you can use it in any role playing game, and it is already used everywhere (with slight differences here and there).

It's not an accurate way of gauging power levels when relevant characters have broken skills and abilities and the author frequently has plot work out in their favor. The falna system is too rigid for DanMachi (or at least Oomori's writing level) and in the end the author writes the story no different than any other shonen

That being said, like Haruhime-chan mentions, the falna system can be used in RPG stories that use some kind of video game growth system, and there are plenty of stories that have that in it