The big turning point and split in D&D that I see is not between TSR and WotC D&D, but between pre-Dragonlance and post-Dragonlance D&D. Dragonlance changed everything.16 years before 3rd edition was released.
Early D&D was the game of dungeon crawling and XP for treasure. OD&D, AD&D 1st edition, and B/X. But then came Ravenloft and the revised Basic and Expert Sets in 1983, and Dragonlance and the BECMI Companion Set in 1984 and there was a really big noticable shift. Dungeon crawling was out, Sword of Shanara, Wheel of Time, and happy pastoral quaintness was in. "You know, for kids!"
When the OSR was a thing back in about 2008 to 2014, the people involved didn't get excited about returning to pre-3rd Edition D&D. It was all about pre-Dragonlance D&D. OD&D, AD&D, and B/X were the names of the game. AD&D 2nd edition and the Master and Companion Sets remained pretty much completely untouched. (I know there was one 2nd ed. retroclone in the works, but that never got completed.)
Forgotten Realms, Dark Sun, and Spelljammer; those are all 2nd edition works. (Forgotten Realms had a few releases right at the very end of 1st, which were all much smaller in scope than the big 2nd edition boxes.) I think there is quite a lot of continuity between 2nd edition and 3rd, which continies into 5th. A greater continuity than what you find in works from 1982 and 1986.