It's meaningless to talk about "good" design or "bad design" without reaching a consensus on what the design question actually is. Designing a car that is "fast" is a different design problem from designing a car which is "fuel-efficient", "easy to drive", "comfortable", or "safe", irrespective of overlap. These are all open-ended design questions, and there's no one true way to solve each of them. Appending the word "objectively" does not erase your subjective biases from the matter, nor does it exempt them from scrutiny. I can assure you that your headcanon on what constitutes "good design" does not necessarily reflect the opinions of other players or even the devs, for that matter. It all depends on how you frame the design question.
The design question may not even be the same across all tanks. Different tank jobs exist to create variations in gameplay experience. Are we looking for a tank that's simple to pick up and play? Complex and unforgiving? One with powerful mitigation tools? Are we interested in DPS potential as MT? OT? Do we want to give the job a certain type of "flavor"? How do we make it fun to play? Do we want unique and niche skills that allow players to creatively solve problems and make the jobs unique? If we do, how do we prevent situations in which those skills become mandatory to clear and give the job a monopoly over a raid spot?
I don't think anyone particularly cares who brings what buffs to raid, so long as there's someone present who can apply them. Delirium/DK is an excellent example of this. It's a mandatory buff. A DRK or a MNK will naturally maintain it through their rotation. SE/DE is a poor example of this. It's a mandatory buff. A WAR will naturally maintain it through their rotation, but it costs the NIN dps to maintain. So you end up being forced to bring a WAR even though two different jobs are theoretically capable of bringing the same buff. This is a team game. You're supposed to cover for each other's weaknesses. If you can bring all of your own required buffs, it eliminates the need for variety.
Skills are generally stance-locked when there is a need to limit their use. In 2.x, IB was the answer to every tankbuster in the game. This does not make for interesting gameplay. Why design a cooldown rotation using long recast cooldowns when you can pretty much use the same on-demand mitigation move for all of them? The 3.0 answer to this was an indirect nerf to IB, through introduction of FC. You now have this incredibly powerful mitigation move which you don't want to use if you can avoid it, since it represents a dps loss. But then why keep it around in the first place? As a safety net for when you screw up your cooldown rotation or can't figure out how to tank it like other tanks do with your standard kit of long-recast cooldowns?
Steel Cyclone is in an even more peculiar position after the introduction of Decimate. We already know that there are plans to replace Wrath/Abandon with a unified system of stacks in Stormblood. I'll be curious to see if these skills will remain untouched during the transition process.
I was under the impression that part of the reason why PLD moved away from a one-combo rotation in 3.0 was to force a trade-off between enmity and dps, instead of giving you an all-in-one combo that did everything for you. WAR's design here is "good" if you don't want the player to exert much effort in thinking about enmity management. But it's only just one a step away from 2.x era PLD design. Sometimes child-proofing a job in the name of "synergy" takes away from making players actually think about their skill usage. But to each their own.
PLD may have some niche skills, but that hasn't prevented players from finding uses for them in Savage. TW has uses in allowing you to dps through the knockback of Gobspin in A10S and Laser X Sword in A11S. Last tier, you could use it to simplify mine knockbacks in A6S/A8S. Before that, it had its uses during the knockbacks in A3S.
Cover is a bit harder to find uses for, but this partly reflects the fact that there is no real equivalent on any other job, so it cannot be "mandatory" to clear. Even still, there were some fun things that you could do with stack-based tankswaps in A5S and A7S last tier, and it was also used to protect your healers from the Goblin Snipers during early clears of A2S. The T13 Earthshaker strategy was another notable, albeit historical application.
In order to design raids that allow for more consistent use out of these, however, you need to widen the toolkit of the other two tanks to allow them to find alternate solutions when there is no PLD present in the party. Access to a silence and the ability to chain stun are other useful skills that could be incorporated into raid design more often if there was wider access to those abilities.
I don't think that these discussions keep revisiting the idea of WAR nerfs merely because of its skill set and how it is constructed. The biggest reason is because of this tired, trite rhetoric about how "superior" the job is, and on how its raid spot security is purportedly attributed to "better design". This is a cooperative game. If your job has a temporary edge, fantastic! All the better for the team, and let's all enjoy it while it lasts. But bludgeoning people with your job's supposed "superiority" ain't gonna impress anyone, and smacks of overcompensation.
Deep down, I suspect that most people don't want to nerf the job, so much as they want to nerf the arrogance that has been built up around it. Sometimes brand loyalty just goes too far. There are plenty of ways in which all three jobs can stand to better. None of them are perfect, and sometimes, merely possessing the slightest shred of empathetic awareness and emotional intelligence is enough to go a long way in fostering amicable, constructive discussions with your fellow tanks.
WAR is a fun job. I'm glad that you like it. I can appreciate that the gameplay gets quite interesting every 90 seconds or so. It feels exciting and powerful to play, whether you're a complete novice or a practised expert. But it's also not everyone's cup of tea, and you're just gonna have to live with that. Sola dosis facit venenum. Bottoms up!