Everything prior to Shadowlands (with BFA being a bit grey), imo, can be considered Legacy WoW. Meaning that all the expansions / storys were connected to demons / titans / old gods (I guess). Yet, Shadowlands onward seems pretty disconnected from that, I think Blizz calls it "new era" or something. Its now Their Story, as the Woke Army that lives to change / promote shit to be inclusive and diverse above all else. I would say the current dev team views Legacy WoW as tainted.
I wouldn't put it that way.
I think the "Legacy WoW" would be the expansions that tied the loose ends left by the previous RTS franchise, basically all the way to the end of Wrath of the Lich King. Vanilla was mostly random villains here and there (Ragnaros was new for WoW, Hakkar was also new, Ahn'Qiraj and C'thun were new) but Naxxramas had Kel'Thuzad and that was a call back to Warcraft 3. Then Burning Crusade tied the loose ends for Illidan, Vashj and Kael'thas, and somewhat Kil'Jaeden, and then Wrath of the Lich King put an end to Arthas.
Then we had Cataclysm which was mostly a made up story which included a known figure from the past (Deathwing from Warcraft 2) but everything else was new. Mists of Pandaria was all new content, then Warlords of Draenor TRIED to go back to the good ol' days of the Horde and failed spectacularly, then Legion gave an ending to the Burning Legion so I guess that could be somewhat linked to the legacy content. Then Battle of Azeroth is all new content and stories, Shadowlands as well, and Dragonflight follows that.
So really the non-legacy stuff goes back in my opinion.. and to be fair some of it can actually be pretty damn good (Throne of Thunder and Lei Shen were amazing in my opinion, despite being part of the kiddie panda stuffs omg.)
As far as the story not being connected anymore to the "old lore" though, I wouldn't say that. For over a decade, WoW has had the main good guys be the Titans and the main bad guys be the Void Lords (the creators of the Old Gods). Thing is, now that we've actually met the Titans (end of Legion), they don't appear quite so unreachable anymore.... and the Void Lords we have never seen but they're supposedly not part of the material realm, so it's this vague threat that's always looming..
What Shadowlands started is it considerably widened the scope of the cosmology of WoW... before we had THE Pantheon that was the Titans, now we know the Titans are one pantheon among many, the Pantheon of Order, presumably made in Zereth Ordus (as we learn in Zereth Mortis that there exist various other Zereth areas in the universe where realities are fabricated). In Shadowlands we met the Pantheon of Death (Zereth Mortis). We also discover Elune is part of the Pantheon of Life (and the sister of the Winter Queen of Ardenweald, from the Pantheon of Death). There are other Pantheons out there, many more deities for various cosmic forces.
It feels a little like how EQ had only those few planes and various deities from the character creation screen or manual, and then when they came around to Planes of Power they had to add a lot of fluff and then after that since the story ended with Zebuxoruk freed and the gods defeated they had to expand it even further out and create new demi-gods and demi-planes and make new people gods (Mayong Mistmoore, etc)...
Dragonflight is going further into the Titan lore, and the main threat so far is the Primal Incarnates, dragons who did not follow the Titans in the ancient times but instead decided to serve the Elemental Lords (themselves serving the Old Gods).
So it's still mostly connected, but they basically pushed the boundaries way back so as not to paint themselves into a corner for the years to come.
Problem is, the writing is mostly shit so it's hard to really care about the lore anymore.
