Luke in ROTJ puts down his lightsaber to face the emperor - the darkest man in the universe.
Luke in TLJ takes out his lightsaber and considers murdering his nephew in his sleep because he MAY turn to the dark side.
sounds like the same dude to me.
You’re missing the key context in ROTJ — Luke almost considers killing Vader which would complete his turn to the darkness.
Yes, but he has that important realization, that he would become like his father, right down to the symbology of the artificial hand. He then lies down his weapon, and becomes a Jedi, thus completing his three film arc. He has passed the test so to speak.