I disagree with this statement. Since the end of TBC we have seen them progress from just straight “magical” addiction.
“Although some elves remain hesitant to abandon their dependence on arcane magic, others have embraced change for the betterment of Quel’Thalas.”
That’s straight from the WoW website describing their changes. They are seeking ways beyond arcane magic. The Reliquary was created as a means to end the magical addiction and is a storyline not really played upon yet. Though we do see them in BFA in Ximbala teaching the Nightborne about archaeology, but also the dig site is specifically an ancient skeleton of a t-rex possible Loa who pre-dated Rezan.
I think the ground work is already in place for the Sin’dorei to rediscover druidism. Whether it be from the old ways of the Highborne or the ways of the Loa. Or hell even the Ar’candor and the knowledge from the Botanist in Night Hold. There’s many paths to point to druidism and it makes sense they would go to it.