It's evident from how equivalent you can set up the hotbars of most healer, tank and melee jobs. Sure the individual actions differ, but you always have stuff like "Every 60s I double weave these two buttons", "X, Y and Z buttons are my after-a-big-raid hit oGCDs", "A is my short-CD oGCD damage weave, next to it is the AoE one", and so on. And it's staggering just how much of each job has direct equivalents in most~all other jobs of its type. Which makes sense, as you say, the 120s meta confines design and since that is quite restrictive, the design space for jobs is severly limited. Coupled with the large job-pool of FFXIV, you naturally run into constant copy&paste situations.