From my understanding, heritage armour quests were first introduced at the end of Legion, presumably to add a bit more context/lore to the newly added allied races, seeing how they didn't have dedicated starter zones of their own. However, they turned out to be so popular with players that people started clamouring for similar quest chains for the existing races, and Blizzard has slowly been adding more of them over time. (If I'm wrong about any of this and you were playing at the time, please do correct me.)
In an earlier Dragonflight patch, Blizzard added a heritage armour quest for humans, which recently came to my attention as I've been playing more, and both my monk and my hunter are human. As I didn't want a repeat of my struggle with the Worgen heritage quest (as mentioned in this post), I decided to do the chain on my monk first. She still had pretty good gear from the end of Shadowlands, and I figured that would make combat a breeze and allow me to focus on the story instead of every trash mob becoming a life-or-death battle. (It worked.) And I was quite impressed!
If you'd asked me beforehand what I expected the human heritage quest to be about, what I consider to be the quintessential experience of being a human in WoW, I would have thought of zones like Elwynn Forest, Westfall, Stormwind, and plots like that of the Defias. And what do you know, all of these feature.The lore around these things has evolved over time, perhaps not always in optimal ways, such as the old Deadmines getting replaced with an updated version in Cataclysm in which the end boss is no longer angry stonemason Edwin Van Cleef but his vengeful teenage daughter Vanessa.
I don't really want to spoil the actual content of the quest chain in detail, but I was impressed by how it wove old and new lore together in a pretty convincing way. After Cataclysm, I never expected to see the old showdown with Onyxia in the Stormwind throne room to ever make a comeback in retail, even if it's in the form of a cut scene cinematic (which illustrates Spymaster Mathias Shaw telling you the story of the Drakefire Amulet). Apparently there are some little variations here as well if your character actually did the Ony attunement back in the day - not that this is something I could test myself, as I didn't have a high-level human back then.
I also liked the bit where you return to Ragged John in the Burning Steppes and his dialogue throws heavy shade at the way the lore around Onyxia's exposure and death has been retconned in the past.All in all, it was a really nice quest chain with a lot of callbacks to some pretty nostalgic moments that also portrayed the way current generation of characters have to deal with the past with a surprising degree of sensitivity. More of this kind of thing please, Blizz.