Many (not all, especially non-free ones) mobile games are gacha games, but even if they are that doesn't mean you have to spend money to win- The games of this sort I play the most are generally generous enough with the free currency / free spins / whatever that I don't feel compelled to do so and I only ever do so if I think the makers of the game are already deserving of any of my money without having to do so. Other games charge for conveniences instead of directly giving you power.
For the record, "energy" was originally put into these games specifically to keep people from playing for too long in one session (not just as another revenue stream, but that's what it ended up becoming) and thus putting themselves or others in harms way by being too distracted by or addicted to their devices. (Then the mobile gaming gods said "let there be paid energy" and there was paid energy)
But I think SE and Nexon both know, if they want people who play this game to play that game, a gacha game isn't going to go over well. Most of FFXI's players have been around since the infancy of the internet and are much less accepting in general of these kind of mechanics.