No, the setting lore as established by Ed Greenwood is still canon, it's in his contract.
That video annoyed the heck out of me, although I wonder if Greenwood's comments were taken out of context. Is Greenwood really irritated over these "mistakes", or was he just being nerdy and pointing out the inconsistencies?
Nothing in the video complained about rose to the level of "lazy writing" to me, but rather artistic choices that deviated from existing canon . . . which I could care less about. I certainly want the Forgotten Realms to be mostly consistent, but don't care about rigid adherence to detailed canon at the expense of storytelling and worldbuilding.
I'm cool with the Purple Dragon Knights evolving into a new style of organization . . . international, even multiversal, and partnering with purple dragons! It's a change that can be done well . . . or poorly . . . and I'm happy to wait until the book comes out before I firm up my opinion. If the new PDKs don't work for me . . . that's okay, I just won't use them in my Realms campaigns. No big deal.
If Sammaster has returned . . . yes, it could totally be a "Palapatine Returns" moment . . . but again, it could be done well or done poorly. And easy to ignore if I don't like it. Doesn't bother me that this "breaks canon" or "disrespects" Sammaster's character arc from earlier stories.
I don't doubt Greenwood when he says his contributions to Realms lore are canon, contractually . . . but I don't care. It's not something that seems enforceable to me, and it's been pretty easy for WotC to simply not worry about it and treat Realms canon as flexible. And I'm good with that. Most of the changes WotC has made to the various settings over the decades they've owned the game I'm pretty happy with, and the few I'm not . . . I just ignore without getting all worked up about it. I think WotC's current approach works well and I'm happy with it.