"Elves aren't mired to the past!"I love how out of all of that quote on elves I pulled from D&D, you focused on "Guardians of the world" and ignored everything else. You ignored where it explicitly says that elves are not mired in the past and stagnant, but use what they relive the past to learn for the future. And you ignored where elves don't change the world because the world will change itself, not because they are against change. The conservatism you mention in your OP doesn't exist in D&D elves as a race, though certainly there can be some individuals who are that way.
writes about how Elves are mired to the past like Elrond thinking of all humans as corrupt like Isildur
"Elves aren't stagnant!"
Elven Society is presented as unchanging and ethereal across practically every setting
"Elves use what they take from the past to shape their future!"
Thranduil refuses to help the Dwarves fight Smaug but gets ready to kick 4 other armies butts in order to take their stuff even though the stuff he wants from the dwarves is stuff they made or stole or whatever from other elves showing that they're capable of holding onto it and also just killed a dragon that he wasn't sure his people could defeat
"Elves aren't against change, they just know the world will change itself without their interference!"
Every Half-Elf's parents had a torrid hidden romance 'cause the elders wouldn't approve of them mingling with other races, often characterized as 'lowering' themselves or being 'doomed' by their love in a setting-reinforcing magical manner
The writers -say- they're not these things, but then make them exactly these things. In various stories of the Forgotten Realms or Greyhawk or Dragonlance it is the actions of Humans and Half-Elves and Hobbits and Dwarves that shake things up because the Elves act in a largely stagnant matter citing past battles and situations as the reason for their continued stagnation and refusal to do things that might upset the status quo, even when the status quo is horrible.
"Show, don't tell" is alive and well in media. And it shows us that Elves don't fit the blurbs and excerpts that get assigned to them.