Depends on job.
Bard rotates through songs while playing proc whack-a-mole. Red Mage every second spell is instant and they try to balance two resources that they need for burst phase, with procs providing some randomness. Black Mage swaps between mana regen mode and nuke mode, has simple rotation but requires movement optimization. Machinist is sorta priority-based, rolling through their combo and using their big cooldowns when possible - highest cpm job at something 40+?
Tanks have simple loop rotations with bursts phases.
Healers have one nuke and dot, so it is more about optimizing encounter gcd usage (healers have powerful ogcds and damage is rather predictable)
Combat starts really slow, but gets more hectic in later levels. IMO FFXIV's first 50 levels are combat/story wise pretty bad. Post-MSQ is huge slog. 1st and the newest expansion in particular have great story. I'd say Shadowbringers is one of best FF games. For MMO, tastes might matter. It is very standard/modern in that sense.