Was it dead on arrival? Is is still playable? Do you miss it like I do?

It doesn't get any better. The final mission is just the WoL final mission with the added bonus of three whining Raynor faggots who can't do anything.

Either Raynor or Kerrigan should have died.
Likely both.
But none of them ever did because of creator waifuwank (Raynor can be seen as a self insert) and because they were too afraid to piss off the fans.

WoL should have ended with Tychus killing Raynor and Kerrigan.
Kerrigan because she's a fucking monster and Raynor because he's lost his fucking mind and tries to stop him.
Mengsk should have then released Tychus as he said he would.
This sets the stage for Tychus to either fuck off somewhere else out of the story (like a mad max folk hero) and let that second in command guy take over Raynor's forces.
Or have Tychus take over. Or maybe just have him come back later on trying to get revenge on Mengsk because everyone seems motivated by that shit anyway.

The other thing that nagged at me is the tutorial nature of a good amount of missions. Like the campaign existed to teach you how to use and micro-manage these units for the multiplayer.

I play heptacraft. It has 7 factions, is still being balanced and only requires starter edition of starcraft 2 to play. It's an improvement.

I gotta agree with this. WoL is a mess compared to BW but it's not bad as it's own thing, plus there are some nice gimmicky missions, new characters, branching upgrades and the Hyperion stuff wasn't bad either. Story-wise it's all over the place but I still kinda liked it aside from some plot holes.
HotS on the other hand goes full retard almost immediately, haven't touched LoV.

Another bit of ranting;

if they HAD to have the Xel Naga in Starcraft why couldn't they have been a playable race?
They could have been something that were super high-tech like the Protoss but would unleash genetically modified creatures as their weapons.

Hit reply too early.
But yeah, their storyline didn't need to be HURRDURR GONNA BLOW UP THE GALAXY.
It could have just been them looking to go further with their experiments with the protoss and the zerg.
They could have wanted to merge the two races to make something completely new.
The Protoss would definitely not want that and while it was sort of the dream of the Overmind to take the protoss into the fold, what the Xel Naga would have planned would have destroyed the zerg forever as well so they don't want that.

And of course the humans, like always, caught in the middle of this interstellar planetary dispute. With the Xel-Naga wanting to "uplift" humanity and, well, space rednecks don't take too kindly to that sort of thing.

Aren't most missions somewhat tutorial like anyway since you are constantly getting new units and the game has to teach you how to use the new units you've gained, I remember this all through Starcraft, although less in the expansion.

You ever play Rome Total War or Medieval 2 Total war? If you enjoy flanking and tactics that's probably worth trying. Just make sure you get the Darth Mod to fix Medieval 2.

Raynor and Kerrigan should have died, and the Zerg Campaign should have been about you playing as an actual Zerg in the competition to create the new 'Overmind' or equivalent thereof.

Because they're the guys who seeded life in the backstory then in SCII the hack writers brought them to the forefront instead of Duran's race being the new antagonists. The Protoss are pretty much made to resemble Xel'Naga by the Xel'Naga hence "purity of Form". The Zerg are "purity of Essence" instead.

Oh and here, have the summary of the last piece of SCII.

Daily reminder that Koreans are subhuman barbarians who had to be civilized by Chinese and Japanese swords