I notice some odd tonal shifts in ROTJ as well. Don’t get me wrong, I love ROTJ, but it feels weird when the film quickly jumps between cute and cuddly Ewoks to Luke and Vader’s dark final confrontation.
That’s probably my biggest issue with Return of the Jedi. We can’t feel worried or scared for Luke when we are constantly are going back to comedic and fun scenes on Endor, and we can’t feel overly amused or excited when we are constantly going back to the Throne Room. Even Revenge of the Sith is firmly “dark” once we reach the end (don’t take this as me saying ROTS is better than ROTJ though).