You're right, It had those positives. And WoD wasn't that bad at first and was enjoyable... It was mostly when It got abandoned, left with a 14 month content draught to make and polish Legion that people just automaticly dumped their collective negative thoughts on the entire expansion, forgetting some of the FEW good things It did, and few they were surely.
To your good points first:
1) Zones and quests were good -enough- they had a cohesive storyline, linearly going from zone to zone and the zones connected eachother unlike Legion's bad zone design which makes legion zones feel unconnected and without purpose to the rest of the Legion's zones.
2) Cinematics were great great, no doubt Blizzard always outdo themselves there.
3) The Dungeons and achivements weren't bad, I just hated the fact they basically took what was early Mythic + but with cosmetic rewards and made It Into today's Mythic + with gear rewards and doing It a thousand times. I enjoyed the other version more from WoD, run a timed dungeon If you're that kind of time pressure loving guy and get a cosmetic weapon or thing, good! But then Legion turning It Into a "Way to progress other than raiding" was utterly and shamefully BAD design.
4) The raids were good really, and ontop of that gear progression was too, you naturally went from normal to heroic dungeons, to LFR level gear from raid to raid, unless you did real raiding then you just had good gear no matter what, you just progressed better than the rest. On that note, Legion's design was aphorant, bad I say. Some might not remember this In their drunken fanboyish haze, but when we did the first LFR in Legion, that being the Emerald Nightmare raid, the gear that dropped for you was worse than what you already had... because, like any other person you were doing World Quests which gave you gear left right and center, and It also gave you a gambling chance to Improve that gear by a few ilevels If you were the lucky one! It's just bad design, bad pacing with gear in Legion, and the rest of what legion did with gear didn't help either, as they're trying to make gear less significant to aquire and Artifact Power/now Azerite more fun to put time Into rather than gear... that was a lenghty one, but I feel every subject needs some explenation or people won't get the point of your criticism.
5) The Idea Is good... but again, they do It poorly. They're not -rares- essentially, they spawn every 5 minutes like any normal mob spawns, even quicker than some normal mobs, only rare thing about them Is they have the wrongly given "Rare" Icon next to their portrait and drop good gear. Rares used to be In older expansions that you saw once a few hours, sometimes days (Which was a bad Idea, hours are fine, not DAYS) and then you maybe got that epic helmet of troll voodoo. Treasure finding Is also too easy, It just shows up on the mini map "I'm here, get me, wohoo.. come here boy get me you..." just flaunting It's loot filled chest like a vixen, not even trying to be subtle, not even trying to hide from the minimap, stuffed away In some hole you'd have to EXPLORE on your own Incentive to find rather than It be shown easily on the minimap and then put on a silver platter in the middle of a giant room essentially Is how you find most treasures In Legion (And In WoD). It makes the treasure and rare finding so trivial It doesn't feel rare or Interesting. This Is criticism for both WoD and Legion as they do It essentially the same, and the rewards Inside aren't even that good, useless artifact power, a piece of string and a golden nugget you sell for a few coppers...
I'm sorry, but even VANILLA through TBC and arguably Wrath WoW had more Interesting treasure finding moments, pretty much every chest back then had like, a proffesion recipe, a few copper ores, a bunch of cloth, a weapon possibly, food and water and some extra things sometimes, or less... and yes that's things people used back then. If you had no use for any of those, sell them on the AH (Yes they got SOLD on the AH back then) and If not there, your guilds will need them to grow their char and help you raiding or PvPing... anything you discovered you disected among your alts, your guilds or the AH. And back then It wasn't as easy as gathering up 10 guys, giving a few cleaves and done. You had to pull mobs carefully one by one, cause you were a noob, some level 21 scrub with a wooden shield and a sword you got from a boar's gut next mountain range over and you need that chest hidden behind 6 regular mobs... but when you fight through to get It, you feel great... unless someone stole It from you, then you ignore him for life. Point Is... much more Interesting to loot chests in WoW In the original game 13 years back than the current version, what kinda Innovation Is that?
6) Legendary quest was... an odd one, I'm conflicted on that still, on one hand It gave you Incentive to run LFR beyond just gear and encourages people to keep playing It, hence learning tactics, hence learning team work and cooperation... hopefully. Which Is good. But then on the other hand, It's basically we are Sauron, we need our super powerful ring. It gave a good story, I'll give you that, so I'll just leave It as It was good enough to keep me Interested In doing dungeons and raids, so I was okay with It. Didn't feel cheated doing the quest.
And now your negatives about WoD:
1) Garrisons were the abolute worst feature for WoD... no wait, It was the BESt feature for WoD, yet they've screwed It up, as It could've essentially been housing for WoW players and not only on Dreanor If It succeded. They should've added customization to your garrison, to personalize and make It your own, removing table missions as well, or at the very least limit It's usefullness back then and put fewer chars to be your companions... which is essentially what you said and I agree with that part. But I think It should've been a personalized housing for players, that was to be worked on properly and more by Blizz, like they promised, bigger more customization and beyond that Is what we were to be given but then just got a generic smaller garrison with -some- buildings...
Now don't get me wrong, It provided many opportunities for this small section of the populace called Roleplayers to play In the garrisons privately, wink nudge hint. Make their own little towns and communities for a few players to live In and that's a good but minor reason garrisons are still even used today.
I think they missed alot by not going far and beyond with the Garrisons, even the Shipyard didn't help although It gave another nice little addition, I kinda wished we could've had our garrison and shipyard next to eachother more closely.. but with our garrison positions being as they are that'd be Impossible to do ofc.
2) One of the two only patches In WoD, and that one was the worst. With 7.1 Selfie camera patch basically, It gave us nothing significant which was sad. 7.2 On the other hand just to point out.. also gave nothing of significance, that's not even mentioning how they 360'ed the story where Grom is the goodie In the end and Gul'dan's the bigger baddie than him. They admited this by the way so stop writing that Into your post.
3) Basically explained In number 1 ^
4) Ashran wasn't the best way to immitate Alterac Valley's success among the people, It failed to be an Alterac and It failed to even be a proper Battleground, but It did well with grinding free Honor and Conquest.. so hooray there. Still wish I could've gotten all the achivements before blizzard fudged me over, but hey, life right.
Lastly as I pointed out above, It was mostly the major content draught that had people go "WoD sucks" despite some good features, some even better than what Legion has now or BfA will have. So I'm sad to say WoD might just be better than BfA also, and Legion will stay on the worst expansion's list forever, at least until we get a good look at BfA... can't wait!