Both yes and no.
I mean, it's a hearty yes because tables make their own lore... or, at least, many do. There's a lot of tables that only use official lore and/or only run modules or whatever, in large part because they don't have the time, energy, or imagination to make their own, or somehow think that anything official is somehow superior to their own measly attempts at worldbuilding.
But it's also a bit of a no because, as I mentioned, every subsequent book will reflect the official lore. That makes it harder to disentangle the lore from the lore. As an example, I had to do a lot of rewriting to make Curse of Strahd fit with my preferred interpretation of Barovia because it added a bunch of really weird things I wasn't fond of (a walled town that ate mostly wolf meat, a town that had weekly you-will-have-fun-citizen festivals, the stupid, jokey epitaphs in the crypt) and removed things I liked (the Red Vargo Trading company, the occult shops of Vallaki, the entire town of Immol, everything I liked about Inajira). So, to keep the to the older lore, I had to do a lot of work, and in the end it felt like a mess. All in all, I would have been better off making my own adventure, but I've given up my dreams of having epic campaigns and realized my strengths lay in a more episodic style of play.
So this goes beyond replacing any slaadi in an adventure with some other monster. I like quite a bit of the new Ravenloft lore from VRGtR, and if I were to start up a new Ravenloft game I'd use it primarily. But if WotC were to put out a new sourcebook or adventure, it would be completely useless to someone who only wants the older lore.
