It's all relative. in XIV they might appear different because the weapons and animations look different but the gameplay and strategy are exactly the same (hit 1 until the key breaks).
I'm really starting to hate people who mention the dreaded "1" key.
I have never felt like I only press one key during battles, unless you count the first 10 or so levels on most jobs. But that's too be expected, really.
FFXI wasn't much better in that regard.
If you compare a THF to a PUP or a BRD or a BST or a BLM or you name it, the way you approach battles is completely different figuratively and literally speaking.
I feel the same way about the Classes (I don't know why that bugs you so much)
On Pugilist, I'm trying to not take damage at all by evading attacks, and returning Haymakers, while debuffing mobs with things like Concussive Blow and Moonrise.
On Gladiator, I'm making sure my shield is always up, and taking full advantage of Phalanx. Curing myself when Aegis Boon is active.
On Archer, I aim to make fights as short as possible, taking advantage of Archer's massive spike damage.
On Lancer, it's all about the TP generation, Stamina use, and what weaponskills you use when you have the TP built up.
On Marauder, honestly, it just feels like I have a lot of HP, and can do AoE damage sometimes. I don't feel particularly special using this class.
That's not to say I don't want improvements and further specialization for the classes we have; I just don't see this massive lack of differentiation that I've seen others talk about.