Even without the additional continents FR is in no way better.
Arthurian knights, ancient Egyptians, 1001 kingdoms, semi modern evil mageocracies next to backward barbarians, etc.
All without ever influencing each other technologically or socially.
This is a misrepresentation of a rather cheap kind.
You claim there's no influence, but the FR, even back to grey box days clearly shows influences and interactions, and you're misrepresenting the actual factions too. There are no "Arthurian Knights". If you mean Cormyr it's a solidly late-medieval kingdom with a heavy bureaucracy, which indulges in mythmaking and is deeply self-regarding but is no more "Arthurian Knights" than RL France in the 1300s or 1400s was. The "ancient Egyptians" - the Mulhorandi - aren't actually ancient, they're just essentially aping older aesthetics and have an Egyptian-themed pantheon, but they use modern technologies, build modern buildings, and have a complicated history that does not, in fact, resemble ancient Egypt very much - you're confusing style with substance. Indeed their history involves significant interactions with other realms - 1/3rd of the human Mulhorandi descend from Thayan slaves, for example. I'm not aware of any "semi-modern evil mageocracies", presumably you intend this to be Thay? But they're not "semi-modern" any more than D&D realms or the FR in general is - if anything they're a backwards compared to The Sword Coast or Moonsea nations or the like. So that's just inaccurate. And what the "backward barbarians" are the Rashemi? Calling them "backwards barbarians" would be like calling the Cossacks "backwards barbarians", and declaring them "implausible", even though they actually existed. Culturally, they're clearly not "backwards barbarians", which is a lazy term anyway, but they're a smaller population living in a harsher landscape, one which isn't particularly built-up or full of cities for resource-related reasons.
I could go on.
And let's be clear:
The FR is not a "well-designed" or "well-conceived" setting. It doesn't feature good links and particularly plausible histories. The damage done in early-mid 2E by just jamming everything into it has never fully been recovered from.
If we're comparing it to Dragonlance, there's an issue. Anaslon and Taladas are opposites.
Anaslon has most of the same flaws as the FR but in many cases worse. The "plains barbarians" are basically a cheap Native American pastiche, but white people have been included as well as Native American ethnicity ones because, frankly, in that era in the US a lot of slightly hippy white people fetishized their perception of Native American cultures (this continues to this day in the South West). And all the other humans essentially seem to be from the same culture, in terms of behaviour, values, and so on, except as influenced by organisations they've joined. I guess there's the sea barbarians, where Black people get to get called "barbarians" (greeeeaaaat) and somehow are Jolly Pirates. I could go on, but arguing FR bad, Anaslon good here is er... at best kind of funny. The FR has a lot of flaws but it has a more plausible setup than Anaslon.
Taladas is a polar opposite. Zeb Cook was clearly really into history, particularly of some places and eras normally glossed over by D&D settings - The Steppes, Byzantium, The Pacific Rim, the "dark ages" (i.e. 400-900 AD), and has societies inspired in part by these and many others, as well as full-on fantasy societies like The Glass Sailors or the Hulderfolk. He also was keen to flip traditional/boring portrayals, with minotaurs running a WRE-equivalent (but a muscular and lively one, not a dying one), the violent, raiding Steppe Barbarians are mostly Elves/Half-Elves, there are relatively well-behaved and reasonable Ogres and Goblins (who are playable - the Bakali don't stray far from trad lizardmen, but make them playable too and they have a real culture), Tinker Gnomes who aren't morons, but a strange isolated steamtech culture obsessed with magma (because they live in/next-to a vast lake of it), depressive Kender, and so on. And there's a real sense of history. Everyone bears the scars of the Cataclysm in a way those on Anaslon do not. Many societies exist directly because of it - the Glass Sailors sail glass plains/deserts created by the blast, the Nylgai-Hadirnoe Scorned Dwarves avoid living underground because their society was all but wiped out by the Cataclysm, and so on. And there are societies with centuries of struggle, or societies that are the product of history, like the Armach-Nesti nation of Elves and humans, which is basically an apartheid state, where a slowly dying-out and inbred group of Silvanesti refugees of the Cataclysm, run a society with the increasingly energetic local humans, who they refuse to breed with (for the same reasons Tanis was shunned), but where the clear implication is, unless they do, their society is doomed.
A starker contrast in worldbuilding is hard to find. Zeb Cook took the ideas of Anaslon and ran with them to a far more interesting and varied place.
Thank you for coming to one of my recurring pro-Taladas TED Talks.