DKs are in such a piss poor state because legion stripped all the tools away and shoved them into separate specs in a way no other class was pruned. The entire DK identity revolved around using multiple resources to activate separate parts of your class, so you were never forced to use just a single ability type.
Rogues, for example, all got to keep things like ambush, but a frost dk completely lost the ability to spread diseases. Fast forward to shadowlands, and nearly every other class was restored to its former glory (think warriors all getting access to stances, ignore pain, etc.), but death knights were screwed by their core designs because the multi-spec crossover was locked behind rune types that no longer existed.
Now, even in DF, we’re still suffering from a bland and stripped down frost and blood dk with UH having every “green” ability mindlessly tossed into the kit for the sake of the supposedly outdated class fantasy aspect of the game that was intended to be unpruned. So still, we are the ONLY class in the game that hasn’t been restored completely because of the way we were separated, and I’ll never forgive it until it’s fixed.
(Just want to note that I don’t want to return to having separate runes, but something more along the lines of death runes for all 3 so that more tools can be viably used. At the very least, a full rework that should have happened in Legion should take place so all 3 specs feel complete and, more importantly, fun.)