I think I would legitimately argue that all four healers have more complex rotations than SMN does because inherently what makes a caster "complex" to me within XIV is how you optimize your movement and casting, and SMN only has that present within like 3 casts in its 60s loop.
I don't care to make the case for all of them because I think it's actually funny when you compare SMN to it's sibling SCH, and how SCH is literally just the old ARR Arcanist's DPS kit still (disregarding all of the removed parts like the Miasma line, Bane and Shadowflare.)
Optimally, SCH has 3 GCDs of non-cast free movement every 60s with 2 Bio refreshes and 1 Swiftcast Broil. Contrasting to SMN's 3 hardcasts per 60s (because you'll Swiftcast Slipstream, leaving you with 1 Ruin III and 2 Ruby Rites) that alone makes optimizing SCH much more complex, and doubly so when SCH's Aetherflow, which is another remaining part of the old Arcanist, is actual resource management with choice inherent in the kit, and SMN's is literally just "press button for damage :O" with zero resource management actually present anymore because of how you save Aetherflow for a minute so you have more to fit into the 2m burst. In ye olden days there was actually decision making in SMN's too because of the trade off between Energy Drain for MP (and 150 potency) versus Fester for flat damage that was double Energy Drain's; I bring that up because it's clearly an intended design of the original Aetherflow to have actual decision making versus what ACN/SMN have as Aetherflow now. Lastly, SCH wants to optimally hit its instant (Ruin II) as little as possible, and optimally SMN wants to cast as little as possible; of the two it is obviously much harder to fully optimize Ruin II out of SCH completely than it is to press Swiftcast and remove a hardcast from SMN's loop.
I wrote that not because I don't think you didn't know or understand that, I just can't believe the actual state of the current SMN lmao. And the fact that 5.0+ SCH is literally more complex than Endwalker SMN, and SCH has a 2 GCD DPS rotation it learns at level 2. The absolute state of this game rn lmfao