Parmandur
Book-Friend, he/him
Well, I was talking about the "5e is the current edition of Dungeons and Dragons and lots of new young players aren't intersted in old stuff" era, not the "Yet another big change and now everything is different again 5e Forgotten Realms era"....but your take on it is actually a very good (maybe even better) one as to one of the barriers of producing more 5e sourcebooks.
My headcannon FR usually post Time of Troubles and doesn't really incorporate the spellplague OR the moondrop. Having never read the SCAG i'm not even sure what changed for 5e other than the moondrop disappeared for some reason.
I'm interested in the semi-official DMGuild FR books released recently but i'm not willing to buy them without flipping through the entire book first. Its interesting they have barely been mentioned in this discussion.
*fixed the marketplace
I'd say that the new players who aren't familiar with the Realms are the precise demographic being well served by SCAG, as it is: it gives a rundown of the whole world, including other continents and the gods, then zooms in the area the official action is taking place in for a deep dive, and has sundry character options. It's a great "only book" other than Core or Xanathars for players who are in a Sword Coast campaign.
Essentially, they undid most of the Spellplague changes, and moved time forwards a little bit. In practice, for most of 5E, they have avoided addressing most elements of continuity that can't be changed by filing off some nameplates (there is a different Open Lord of Waterdeep than in 3E, but changing names and adopting Dragon Heist to a different timeframe is trivial). Perkins has said this is a very intentional strategy, given the splits in the FR fanbase, and the desire to not bring canon wars into the picture for newer folks.