Many try to claim that Lucasfilm went too far by introducing aliens/inter-dimensional beings into the storyline. I would agree with those people, but then I’d be wrong also.
Previous films have revolved around a golden box that melts faces, voodoo, and a mythical cup that grants eternal life/heals wounds/doesn’t affect baldness. Introducing an alien plot in the era of Roswell and Godzilla fits perfectly in the series.
Kingdom of the Crystal Skull is the best entry in the Indiana Jones series. Written by the screenwriter of Jurassic Park, the storyline is the most compelling of all Indiana Jones’ adventures.
In The Last Crusade, Dr. Jones tells his students that “70% of all archeology is done in the library.” As he and Mutt Williams drive through the Marshall College library in KotCS, Jones tells a student that if they want to be a good archeologist, “you gotta get out of the library.” It shows how his character has changed through the years.