Fair enough. Like I said, I didn't play essentials. I've just seen folks who did say it was 4e's half edition change.
See, lore to me isn't really what makes an edition the edition. Changes to the rules are what makes an edition an edition. Drastic enough changes and you have an entirely new edition. We could have had nearly identical lore throughout all of the editions, with the only necessary differences being when new classes and such came into being.
For the most part, yes. If you'll allow me to expand the point, the issues come when the lore =/= the mechanics. It creates a mental disconnect. And to be sure, often the lore has not lined up with the mechanics, throughout D&D's history. They've certainly
tried to do so, or at least tried to make justifications for the shift (see Time of Troubles, Spellplague, etc.), but you're always going to be left with things that just make no sense from a lore, in-universe standpoint.
Now you can build a game where it's rules and lore are closely associated with one another. Earthdawn is one of my favorites for this, where if you told an NPC that someone is a Fourth Circle Warrior, they'd very likely understand what you're talking about (unlike in D&D, where if I told someone that a guy was a Fourth Level Fighter, I'd get funny looks).
But because D&D has evolved in such a way that it is meant to be usable with different settings and lore, you run into problems. AD&D tried to make such adjustments, with things like Oriental Adventures and Dragonlance Adventures with special rules and custom character options, and we still see a little of that to this day (like with the MtG setting books), but modern D&D has become a more generic system, where it's intended to plug and play into many possible settings, but there will be cases where it's a square peg being driven into a round hole.
Dark Sun was written with 2e Psionics in mind- it feels very different without those rules. Eberron was written with 3e rules in mind- and again, it feels very different in other editions as a result.
For example, 2e Tieflings were part human and part "something else" (where the "something else" was assumed to be Lower Planar in origin) and thus could have wildly different appearances, and, eventually, abilities. By 4e, Tieflings had a default appearance, later retconned as due to meddling by Asmodeus.
Today, Tieflings are organized into major "bloodlines".
Halflings used to be Hobbits with the serial numbers filed off. 3e made them slighter and longer limbed, 4e introduced lore making them nomads who travel in caravans or along rivers. 5e went backwards a bit, but also introduced the "top heavy" Halflings.
Someone who wishes to bring their Halfling Fighter/Thief from 1e Forgotten Realms to another edition may start to wonder who the heck these pretender Halflings are, wearing shoes and such, not to mention having their abilities drastically altered! "What do you mean I lose my infravision! I have Stout blood, you know!".
Generally, we're supposed to not dwell on such things- treating them as if they always were the way they are now, unless otherwise specified. Having devoured a lot of Faerun lore in my AD&D years, it's often surprising what's been changed and what's been forgotten.
I remember playing a 4e FR adventure in Encounters that took place in the same geographical location as the Baldur's Gate: Dark Alliance video game, yet nothing about it was the same. When I asked the adventure's author on the forums, he was completely surprised- as far as he'd known, it was basically an undeveloped space he could easily drop his adventure into!
We might like lore to line up with the game mechanics, but not only has that ship sailed, D&D has become a veritable Ship of Theseus. It still has the same general shape, but very few of the original parts.
Yet, at least from one subjective point of view, it's still Dungeons & Dragons.