"Hope in the face of failure" is the theme of all of Star Wars in general. The first movie is literally called A New Hope. The second is about how this new hope fails in his role as the new hope. The third movie is about how Vader finds hope from within the ultimate failure of falling to the dark side. There was an entire prequel trilogy devoted to the failure of Anakin, the Jedi Order, and the Republic that eventually required a new hope.
The Last Jedi says nothing new about failure or hope. Everything new it has to say is in how it deconstructs Star Wars' long established theme of failure and hope. It shows different, more irreverent kinds of failure than what you would expect to see in high fantasy (hence why Luke milking sea cows was so important to Rian...it wasn't just failure he wanted, he wanted debasement of the grand fantasy archetypes), it makes the failure more critical of standard hero archetypes (in Luke and Poe's case), or built around subverting expections (Finn and Rose's side plot is designed to feel like the kind of side plot that would end in success so that it can properly feed into the main plot).
"Failure and hope" is a theme of TLJ, just as it's a theme of all of Star Wars, but what it really cares about is deconstructing that theme (along with plenty of others).