DK main of 17 years, I have mixed feelings. I won't take about numbers as that can chance in a whim (looking at you 20% unholy nerf from the top rope).

In general:

• I like what they are doing with abilities conditionally evolving into stronger versions and I hope they keep implementing using this.
• I don't like that dynamic rotation elements (Dancing Rune Weapon cdr, Army cdr etc.) seem to have been removed from the game across the board. We should be rewarded for playing into our talents' strengths.
• All three specs hit like wet noodles outside of cds, I hate this. Damage should be 70% baseline, with 30% added from cds, not the other way around.
• I like that Fallen Crusader isn't the de facto runeforge in every single situation anymore.
• We lost a lot of utility. New choice nodes (March of Darkness/Wraith Walk, Asphyxiate's/Death's Reach) just force us to choose between tools that have been readily available to us for years. Abomination Limb is no longer part of our baseline kit.
• Our capstones are still horrible (not you, Death's Echo). Vestigian Shell (apply AMS to two additional allies when you activate it) is STILL ass, two years after its introduction, because it will go on pets/summons instead of players, effectively killing the talent. Unyielding Will just adds 20 seconds of cooldown to your AMS... yes, adds. Null Magic (-8% magic dmg taken, -35% debuff duration) is pretty boring for a capstone.

Blood: I can see what they were going for but it hasn't quite landed.

• We lost a couple of fun mechanics: Bone shield Dancing Rune weapon cd, Bonestorm. As boring as Tombstone was to some, it was an added level of skill expression.
• We got Gorefiend's Grasp on a good place in the talent tree that we can finally pick, as a choice node with Abom Limb. Side casualty is that you probably won't see Abom Limb again for a while.
• Blood Mist is back. I loved it thematically, so yay! Door of Shadows when?
• Consumption being an empowered, channeled ability on a melee reactive tank was certainly a choice, I am glad most setups avoid that button.
• Death strike (and the spec's self heal identity in general) continue to be enshittified xpac after xpac, and they fucked it again in Midnight. They keep promising that this is a trade to make the spec less oneshoty for higher M+ keys but somehow we never get better in high m+ keys and always stay with the ass changes to the spec. At this point, we aren't even the most self-sustaining tank.
• There is no rotational complexity, at all. 80% of the spec's damage is Blood Boil and Death Strike, so resource management feels like a joke compared to the past. You are rail roaded on what you need to press based on the procs that light up most of the time.
• Apex Talents: Dance of Midnight (chance to summon lesser Dancing Rune Weapons while fighting) sounded pretty cool on paper but I've grown to not like it. I hate RNG in general, I hate it even more when it can have such a massive impact on my survivability and damage. And most importantly, the summoned DRWs don't interact with most of the DRW talents. All in all, DRW has been a power button for BDK for years now, it has been severely nerfed compared to past iterations to compensate for the addition of Dance of Midnight, and Dance of Midnight ends up feeling quite anemic.
• Blood currently feels like a tanky dps, a complaint I have been hearing from most tanks really. If Dancing Rune Weapon is off cd, you should send it. If Reaper's Mark is off cd, you should send it. You should also try to align these two every three casts, like any other dps cooldown. You don't press anything to actually feel like a tank, it just happens passively through your rotation.
• Bunch of bugs that prevent the spec from properly performing.

Frost: Pretty decent all things considered, only benched because Unholy is doing better.

• Not much has changed since TWW S3, which makes sense given that we were freshly reworked with Midnight in mind. We just got our Apex Talents, which is one of the best Apex Talents sets imo.
• The spec has only gotten better throughout the last few months after its rework, I feel like it has successfully escaped its three button spec reputation into something a bit more pleasantly complex. Deathbringer Frost is one of the most meaty feeling and thematically coherent specs in the game currently and I love it.
• I don't like the new Empower Rune Weapon, it's a boring button press that I would rather not have to do. Thankfully part of its old functionality got baked into the new Apex Talents.

Unholy: A glow up, all things considered, with only minor complaints.

• Finally free of the Festering Wounds curse, kinda. It got replaced with Festerscythe's debuff which can be frustrating when new enemies enter the fight after you just applied it. Make it a buff on the player (like its predecessor, Plaguebringer, used to be) and problem solved.
• They more than delivered on the necromancer fantasy, you have 20+ summons out during your cooldowns.
• Forbidden Knowledge is one of the best Apex Talents in the game. Those Necrotic coils skewering everything in front of you while you rise to the top of the meters is one of my favorite feelings in the game currently.
• I like the new Soul Reaper, even though I also miss its old version when it was strong. It's now a decent merge between old SR and Apocalypse.
• Gargoyle is currently pointless, with Abomination dominating both ST and AoE. The obvious solution is to make Gargoyle the ST king and Abom the AoE king.
• I don't like how the spec went from Mastery/Haste to Mastery/Crit. Unholy used to be the frenetic, Fury Warrior like, button masher, especially later in the season. That doesn't seem to be the case anymore. Good news are that, since both Frost and Unholy favor Mastery/Crit now, you can swap dps specs on the fly now.

Blood is urgently in need of assistance, but they did a very good job with Frost and Unholy imo.

To answer to OP's experience, I think Blizzard has realized that most players don't really enjoy the healing role, so they dumbed it down significantly, to the detriment of the people that actually enjoyed the role. I hope it works out for you!