Doesn't the Soul Crystal have Relevance though?
Like, we are using the memories of Past Users to Teach us the Skills we are using.
And in tern, we are instilling our Knowledge and Experience into the Soul Stone.

--Spoiler--
Even Alphi when he becomes a Sage, is given a Soul Crystal to instill him the knowledge and Skills to use those Weapons.
So in case we have forgotten, Endwalker Reminds us why we have them in the 1st place