Some dev art was released exploring the concept of climbable surfaces waaaay back in alpha, but I think it’s been on the very crowded back burners for a long time since we have grapple hooks and stairs and portals for navigating vertical heights.
I believe that right now the philosophy that is used to determine what to invest development time into next is along the lines of “what will have the best impact on the most players” is developed first. While I have no idea what is and is not currently in development, I am willing to bet that ladders will remain on the back burner for a little while longer.
Edit: there was also at some point the idea that maybe you chisel a block to make it climbable by cutting foot and hand holds into the surface… I like that it could be paired with an undo chisel to make walls temporarily climbable during construction and then undone afterwards.