Its retconned to shoehorn in the new dieties, the new cosmology, the new races and classes.
Again, you're using it wrong.
I can't seem to recall many new deities, as the primary complaint I've seen is that they cut down the number of deities by making redundant ones aspects of other ones (thus, Talos was an aspect of Gruumsh). That is, indeed, a retcon, since they have stated in the past that each god was a distinct entity.
The new cosmology is not a retcon, because it came to be during the 100 years between 3rd Editon and 4th Edition. So, 3rd Edition's Tree/River/Mountain cosmology was how the planes were setup in 1385 and earlier, but because of the death of Mystra, the destruction of the Weave, and the Spellplague, that
changed. The plot moved forward and the world changed. That is not a retcon. You want to see a retcon? Look at 3rd Edition's FRCS, which changed the Great Wheel from previous editions into something new, and the 3.5 FRPG, which made it into the Tree/River/Mountain.
New races are a yes and a no. Yes, they retconned certain types of elves into eladrin and elves. No, the dragonborn were not retconned into the Realms, as they arrived after 1385 because of the Spellplague. Elves, retcon; Dragonborn, story progression.
New classes are not retcons. There's no indication that they're saying "Hey, there have always been warlocks." Wizards work differently because of the death of Mystra and the change to magic. Back in pre-1385, classes were like they were in 3.5, but they changed because the world changed. Not a retcon.
Sure.....but overall is it storyline movement? No not even close.
Good to see you can make a judgment on two 100+ page products without actually having read them. Rock solid.
Perhaps retcon is a poor word.
It's a good word when used correctly. The problem is that it gets used incorrectly all the time, since people often simply apply it to things they don't like, rather than things that were actually retroactively changed.
Shoehorned? Crammed? which word would you like to use that shows their shoving in elemental primordials, new races, the new cosmology and so on.....because its sure not a real progression.
"Addition."
Unlike you, I'm not upset about a new edition of a product, with timeline advancements, actually being different or including new stuff.