A couple of thoughts on Indy 4 **spoilers**
1) On Sounds: The traditional John Williams soundtrack was woefully underused. And maybe I'm the only one who thinks this, but the problem wasn't that Harrison Ford looks different after 19 years away from the role; it's that he SOUNDS different. When I first heard him talk, it was like a different actor. I suppose it makes sense because voices change with age, but for me, that rather than appearance was the most jarring aspect of the Indy character in this movie.
2) On Iconography: There are two icons in the Indy movies - the relic Indy is hunting, and Indy himself. Neither is very strong in this movie. Most viewers will understand Western iconography more than . . . well, Asian or South American iconography, and therefore, it will resonate more. It wasn't a coincidence that the first two movies seem more coherent for their use of the well-known Christian icons, the grail chalice and the ark of the covenant (forgive me for that, as the ark isn't actually a Christian archetype, really, is it).
So when the icon in this one is a crystal skull (born of a myth created in 19th century Britain and perpetuated by 20th century new-age ritual, neither of which feature prominently, or at least, with much explanation, in the movie), surrounded by Meso-American/Southern American imagery, it naturally won't go over as well as the Western icons. Additionally with the Western icons, the treasure hunting is more familiar; descending into a church in Venice after reading a code out of stained glass resonates with an audience. Descending into a pyramid in Peru, not as much. Also, any puzzle solving relating to the non-Western icons will need more exposition, which is notably absent.
In addition, Indy himself isn't as strong a presence in this movie. In the two better movies, there's an inner search within Indy himself as well as a search for the treasure; in Raiders, it was his relationship with Marion. In Last Crusade, it was his relationship with his father. In theory, in this movie, it's supposed to be his relationship with Mutt but that's a bit lost in the movie, which is in part due to the lack of exposition, and also in part because of the re-introduction of the Marion character.
As if the lack of solid support around Indy to bolster his character wasn't enough, there was apparently reticence in giving Indy much in the way of action scenes. While he is certain in all the action scenes, Indy is really only at the center of a couple of them. And he uses his whip all of . . . twice? Three times? There's enough camera work on his fedora . . . but barely any on his bullwhip.
3) On Post-Modernism and Deconstruction: The movie is full of bits and pieces of the previous trilogy, as if scenes from those movies were like potsherds and cobbling them together could make this movie a new pot, or something like that. It doesn't really work. What ends up happening is that every once in a while, the viewer is jerked back into the past, by the sight of something from the previous movies, a camera shot reminiscent of Raiders, or the Ark itself, or pictures of Brody and Jones Sr. (a bit heavy-handed, that scene).
The only time it's effective is when Indy restrains Mutt before they explore a tomb, kind of a reference and yet not exactly a copy of when Indy restrained the Alfred Molina-character in the beginning of Raiders. The update was a cute reminder that this was still Indiana Jones on the screen. And a very necessary reminder too, because even though Indy scoffs at the suggestion that he's softened in his old age, there's clearly a "get off my lawn" kind of feeling to many of his lines.
The other times when the movie gets self-referential, it's actually kind of pitiful, which makes me think that when the filmmakers were making it, they wanted it to be purely nostalgic, and for us to understand that there is no going back. When Indy packs his case in this one (contrast with Indy packing in Last Crusade to go to Venice), it's not to go off on an adventure; his shirts are pressed, and he doesn't end the scene by throwing his whip and gun into the case. Indy is quite literally dragged into this adventure, and we're made to understand that unlike the heroes who ride off into the sunset at the end of Last Crusade, the passage of time turns all heroes into dusty relics sooner or later, until all they can do is find what happiness they can and pass the torch onto others who will continue the exploration.
4) On Espionage and Warfare: Spies don't really have any place in the Indy films; there's good and there's evil. So when we turn to the Cold War-era and we introduce a spy, it throws kind of a cog into the wheels of the film.
One of the romantic aspects of the previous Indiana Jones films was the idea that despite modernization (planes, trains and automobiles . . . see the red lines on the map, and the sheik in Last Crusade going ga-ga over the Rolls Royce rather than gold trinkets), there was always a place for Indy to explore, and somehow, something Indy would find there would be dragged from the past to have an impact on the present and future. With the introduction of psychological warfare, spying, and things like Red Scare, the relic that Indy hunts is less related to the present. It serves as an interesting metaphor, to be sure, and it's explained as a potential weapon, but the crystal skull hardly has the gravitas that the smiting power of the Ark and the immortality of the grail held. Indeed, it doesn't even look like the huge hunk of quartz has much heft to it when the characters handle it; shouldn't that thing weigh about 30 lbs?