Perhaps I missed but how is magic dependent on the Weave of Mystra? I mean she doesn't even exist in my setting!

Seriously though:
- I don't see any reference to the Weave in the PHB Chapter 7: Spells (I didn't check every spell though).
- I don't see any reference to the Weave in the Wizard class description. It simply refers you to Chapter 7 (see above)
- The Weave is not included in the DMG "Lore Glossary" or anywhere else I can see.
- There is no mention of the Weave in the MM spellcasting description. I did not check every monster's lore but there was no mention of the Weave in the lore of: Arch-hags, mages (apprentice - archmage), or the lich.
So how exactly is WotC making all magic dependent on the Weave? From what I can see it has no impact on how magic is used in 5e24.
"One D&D" is both 2014 and 2024 together. And in 2014 they included this:
The Weave of Magic
The worlds within the D&D multiverse are magical places.
All existence is suffused with magical power, and potential
energy lies untapped in every rock, stream, and living
creature, and even in the air itself. Raw magic is the stuff of
creation, the mute and mindless will of existence, permeating
every bit o f matter and present in every manifestation of
energy throughout the multiverse.
Mortals can’t directly shape this raw magic. Instead, they
make use o f a fabric o f magic, a kind o f interface between
the will of a spellcaster and the stuff o f raw magic. The
spellcasters of the Forgotten Realms call it the Weave and
recognize its essence as the goddess Mystra, but casters
have varied ways o f naming and visualizing this interface. By
any name, without the Weave, raw magic is locked away and
inaccessible;the most powerful archmage can't light a candle
with magic in an area where the Weave has been torn. But
surrounded by the Weave, a spellcaster can shape lightning
to blast foes, transport hundreds o f miles in the blink o f an
eye, or even reverse death itself.
All magic depends on the Weave, though different kinds
of magic access it in a variety of ways. The spells of wizards,
warlocks, sorcerers, and bards are commonly called arcane
magic. These spells rely on an understanding— learned or
intuitive— of the workings o f the Weave. The caster plucks
directly at the strands o f the Weave to create the desired
effect. Eldritch knights and arcane tricksters also use arcane
magic. The spells of clerics, druids, paladins, and rangers are
called divine magic. These spellcasters’ access to the Weave
is mediated by divine power— gods, the divine forces of
nature, or the sacred weight of a paladin’s oath.
Whenever a magic effect is created, the threads of the
Weave intertwine, twist, and fold to make the effect possible.
When characters use divination spells such as detect magic or
identify, they glimpse the Weave. A spell such as dispel magic
smooths the Weave. Spells such as antimagic field rearrange
the Weave so that magic flows around, rather than through,
the area affected by the spell. And in places where the Weave
is damaged or torn, magic works in unpredictable ways— or
not at all.
Now you can say "That's not in D&D 2024's book!" all you like. But it's there, in a whole block in 2014. Which was the guiding principle for everything that lead to 2024's edition, which they've repeatedly said is not a "New Edition".
When they say this part of the 2014 book is no longer relevant or canonical or whatever specific term they want to use, great. Until then it's still in effect as far as I can tell.
And, at the very least, it was a pre-2024 stumbling block to making Dark Sun or any setting which didn't have the Weave or some equivalent.
I agree, but I don't feel the complications are vastly different* than any other new /old setting. If they want to do it, they can. If not, they will not to do it.
Ehhh... I think a setting that goes WAY HARD away from traditional or "Standard" fantasy is going to be a bigger problem for them to get past the board of directors.
After all, Theros sold less than 40,000 hard copies. And we know it sold 14,000 copies in the first month because it was a Hardcover Fiction best seller in July of 2020 from links on the Wikipedia page for it.
That said, I hope a 5e Dark Sun sells a million copies. I love the setting. I just don't anticipate it would sell well compared to Ravenloft.