Dark Knight is playable, but BORING

[Satarn]

Chances are the people that find current DRK dull don't actually know how to play it very well and assume Edge/Flood = Mash on cooldown buttons and then do nothing until you get MP to mash it again.

Oh boy, the irony...
No dude - this, this right here, is how people complained about SB DRK "mindlessly spamming DA on everything all the time".

People who complain about current DRK are, for the most part, those who knew and liked the resource management and pooling and are dissatisfied with how that aspect of the job has been in fact diminished(as well as the considerably lowered APM required).

Before you needed to constantly manage your MP/Blood to avoid overcapping, while still keeping most of it for party buffs. Now the job is actually way more linear like PLD/GNB, because all cooldowns and the rate at which you gain MP have been made to naturally align with said buffs, requiring very little management. The way everything is calculated, you regenerate entire bar of MP within a minute, which aligns perfectly with emptying all that into Trick Attack for example.
It's not that noticeable without a NIN, but the other buffs you get to work with are on two and three minute cooldowns, so you still pretty much operate on that minute-to-minute basis, with not much else in between.

Moreover, SB removed all interaction between the two resources - you can no longer spend MP to gain Blood and vice versa, which really hurts the synergy within DRK's kit and further simplifies the management aspect.

But DRK has literally ALWAYS been about heavy resource management. That aspect has NEVER changed.

It used to be "heavy" resource management. I'd say now it's more on the lighter side and that's the issue.

It's drastically different. In SB you wanted to avoid TBN usage because DA was almost always more of a gain per MP than TBN was.

Except that was not actually the case. The whole TBN+BS vs DA issue was pretty complicated on the case-to-case basis, but overall it turned into being DPS-neutral over the course of the fight, as long as you didn't spam it literally on cd.
In fact you were more encouraged to use it on raidwides and even autos in between other cds, simply due to it being more likely to break than now and hurting you less if it didn't.