That about sums it up. Though in terms of things like Airplane! showing gratuitous titties as a sight gag in and of itself, I think that was one of the precipitating reasons for creating the PG-13 rating in the first place, around 1982 or 1983: there were movies that studios wanted to distinguish from “Rated R”, yet which parents were upset about having “those one or two sexually suggestive/explicit scenes we didn’t appreciate our younger kids seeing”.
I remember going to see the movie Red Dawn in theaters specifically because it was the very first “Rated PG-13” movie ever. I happened to turn 13 just before it came out, so I could go on my own (with my friends), and was hoping for some sexually suggestive/explicit stuff. I’d have settled for a gratuitous titty sight gag, really. What I got was a story about survivalists saving America from parachuting Russkies. What the hell?
To your point, that very sentiment - “I’d like this rating bumped up a notch because there were these one or two scenes we didn’t appreciate our younger kids seeing” - has shifted basis in the past 15 years. Not only are parents somewhat more protective of their kids’ emotional fragility these days, far more young kids (under age 10) see movies at home than by going to a movie theater.
So where it used to be that you’d assume a G rating for “General Audience” meant “people bringing their minimum well behaved 6-8 year olds to a movie, because who the heck would pay to bring a 3 year old with a 20 minute attention span into a dark theater”, now it means “can I put this on the TV for my 3 year old to keep him/her occupied while I work on my laptop and not have the child get upset or warped?”
And while the VCR began the era of home video watching, I’d say the ability of very young kids to watch Netflix on a tablet is also a factor. You can install “rating filters” on devices for kids still too young to figure out how to bypass them, but that’s a pretty young age these days, so “G” and “PG” really have to mean G = 3 year olds and PG = 8 year olds.
The first I ever heard of the 1999 David Lynch film The Straight Story was a radio advertisement while I was in a cab. I wasn’t paying much attention to the ad, but was aware enough to realize it was an ad for an upcoming movie.
At the end of the ad the voiceover reads “Directed by David Lynch. Rated G.”
My ears nearly expanded 200% in diameter and my eyes nearly bugged out of my head. I immediately said to myself “I have got to see this movie!!!” just to find out what a David Lynch Rated G movie would be like.
ISTR that PG-13 was created more to address issues of violent content in movies than nudity; the PG-rated film which is generally pointed to as a catalyst for it was “Indiana Jones and the Temple of Doom.”
The Eagle Huntress is a documentary about a young Mongolian girl who learns to hunt with a golden eagle. I’m a little surprised that it is rated G simply because of the scenes of the eagle ripping a fox apart. But G has been the kiss of death for a lot of great movies like Carroll Ballard’s Never Cry Wolf, which featured a scene of a naked Charlie Martin Smith.
One of my favorite films, Topsy-Turvy, had an incredibly gratuitous nude scene and f-bomb just to get an R - apparently thinking it was necessary to be seen as a “serious” movie.
OK, here is the thumbnail review from Common Sense Media, which is explicitly about rating and reviewing movies regarding their child-friendliness and which isn’t either the MPAA or some gonzo Jesus Freak outfit:
The bolded part is the rude humor (or, well, rude humor and romance between a husband and wife) and, as I said, the rudest part is part of a song that’s on the radio.