I think that's true. I'd also want to add that the other movies since RotJ have good and valid reasons for not being as fun.
The Prequel Trilogy
They fail every other measure of good storytelling, so why would fun factor be any exception?
The Force Awakens
Bringing Star Wars back to its roots with a very specific balance of drama, whimsy, and nostalgic references after the prequel trilogy knocked it far off course. A sustained lighthearted tone isn't the right note to hit when you've got to establish a new set of heroes and villains, and conclude Han Solo's storyline.
The Last Jedi
Establishing or further refining the dramatic and thematic foundations of the sequel trilogy, positioning Rey and Kylo for the final film, and cementing Luke's legacy in a meaningful manner by showing him finally overcome his demons and become a galaxy-wide rallying point for the next generation of Jedi and Resistance allies.
Rogue One
Following the crew of a suicide run to nick the plans of the defining superweapon of the Star Wars franchise, all for the hope that one day the Alliance might use them to destroy the Empire's planet-killing abomination. Portraying the Empire at the height of its might. Lending additional value and thematic resonance to Luke's victory against the Death Star in A New Hope.
Solo is garbage, but Rogue One is probably the worst movie I've ever seen.
These takes be piping hot.