The rotations are simpler (8 button total for most classes) in Lost Ark but the catch is that most skills have animation lock and also move your character around, which means you'd have to think a bit more on when and how to use your rotation. Boss patterns are also random so you have to constantly think on the fly. Every button on a class in Lost Ark has a different hit AoE (think pre-6.1 Overpower vs. something like Total Eclipse) so you need to aim your skills. They also have a lot of different attributes. Bosses can CC you and slam you on the ground causing you to fall over for 3s, but some skills have Super Armor which you can use to give yourself CC immunity, which means that you can adjust your rotation on the fly so that you keep uptime with Super Armor by using those skills to give yourself uptime.
But really what makes it more fun is that every skill feels like they do something different and you're not just hitting a dummy because the boss attacks are random. FF14 is a choreography which is fun when fights are as complicated as DSR which I'm doing right now. But when bosses do like one mechanic every 20 seconds it honestly feels like a slog. Lost Ark bosses are mechanically simpler but they feel more engaging because of the randomness and because the skills all do different things and aren't just filler damage. Lost Ark has easier fights, but they feel more engaging. I think FF14 can do the same. Give players lots to do but make it not punishing at all when you fail.
