I love both the Murderbot books and Piranesi. I think they're excellent for _very_ different reasons.
With Murderbot, the "corpos control everything" scifi future setting is nothing new. I think the brilliance is in its portrayal of the main character, primarily through its inner voice. Murderbot is a really unique character and it is written very well.
Conversely, in Piranesi, the main character is basically a cipher. He doesn't know who is, and we don't learn a lot about him or his psychology for most of the book. I felt like he was mostly there to let us experience the world, which as you put it was otherworldly and quite unique. The brilliance of the book is the prose and the world, not the character.
But like I said, I think comparing anything to Dune is pretty tough. Dune is a landmark work that still influences modern writers, and that modern audiences still enjoy reading. The recent movies have translated it to the big screen and captured an even larger audience (an amazing feat given how weird the books are).
Very, very few SFF books have had a similar impact. There's Tolkien, who is arguably the most influential SFF writer of all time. What other SFF works from the 60s or earlier are still as widely read and influential as Dune and LotR? Almost none, except Le Guin's Earthsea books, which barely squeaks in with a 1969 release for the first book.