The main reasons behind the dissatisfaction of job gameplay

[TemporalFruitsAndVeggies]

Complexity in Heavensward wasn't what I'd call artificial. Game knowledge carried you very far back then, skill expression was available and jobs had identity and nuance.

What we have now is completely artificial difficulty, I wouldn't even call it complexity. There's just 'do damage', 'increase damage', 'take less damage' and 'heal for X' abilities now, no nuance, no complexity, no skill expression, no gameplay. The whole game is basically on rails.

That's fair. I'll defer to you, then, because I honestly don't remember too much about Heavensward because it was so long ago. I mostly remember the Machinist's ammo system, since I mostly played Machinist, but I can't remember if it was meaningfully more complex, or just different.

[Aravell]

That's fair. I'll defer to you, then, because I honestly don't remember too much about Heavensward because it was so long ago. I mostly remember the Machinist's ammo system, since I mostly played Machinist, but I can't remember if it was meaningfully more complex, or just different.

Complexity is difficult to define as what one finds complex may be simple for another, so let's speak of nuance and identity instead. Let's use MCH since you're familiar with it.

MCH in HW had multiple abilities that interacted with the kit and had their own nuance on when to use them. Gauss Barrel increased your damage BUT also gave you cast times, Rapid Fire made every action instant for the duration, ammo affected your shot combo and Wildfire compiled damage instead of total number of hits. Already we can see that HW MCH had a kit that interacted with itself and had a strong identity as a gunslinger with a turret.

Now we see MCH in DT. All the tools are disjointed from your main filler, you don't even use your main filler during Wildfire anymore, there's no more ammo so you cannot manipulate your kit, Hypercharge is just artificially forcing you to single weave, and Flamethrower is just completely worthless. No nuance, weak identity, job on rails.

[Valence]

That's fair. I'll defer to you, then, because I honestly don't remember too much about Heavensward because it was so long ago. I mostly remember the Machinist's ammo system, since I mostly played Machinist, but I can't remember if it was meaningfully more complex, or just different.

HW MCH was considered the hardest DPS job for a reason. There was probably a lot of artificial difficulty in that it had literally 3 or 4 buffs with different recasts, and a crapload of damage ogcd that were doing different crowd control effects but ultimately were mostly used as ogcd damage spamm.
But then there was also just how wildfire bursts worked, and rng pattern recognition and management with ammo management, and this alone was a lot of decision making and agency, and was kept and improved on for SB MCH, while the excessive amount of obnoxious buttons was culled and the proc rate made a lot more bearable and less miserable. However it lost a LOT on the party resource support and turret management, but that's also on SB that already simplified the battle system on that front as well. But besides the loss in party resource support and interaction, which was big don't get me wrong, SB MCH as a rotational kit interacted with itself even more than it did during HW especially due to its unique gauge system.