I’m referring more to the OT in this regard, and yes, TFA really started the trend - ‘Who talks first’ and the joke about Daniel Craig dropping his weapon probably counts here - but overall the characters take the situations seriously and it goes a long way to legitimizing even the more absurd moments of the movie.
In comparison, Boyega has pretty much patented a look of baffled skepticism with regards to TLJ’s dumber moments:
When your co-lead looks embarrassed with the BS, you’ve got a problem.
You mention Space Leia, Rose, and Canto Bight as being very earnestly implemented and I agree. Rian seems quite interested in being serious in the parts of the story that he likes, while treating the bits he doesn’t like as punchlines. Just little things like Anakin’s lightsaber, Snoke, Maz, Hux…