As I said, my theory is that all elements are just so tired. The fight on the convoy was pretty amazing in Raiders, but subsequent action movies have raised the bar so much that the similar sequence in the jungle (which also owed a lot to the jet-bike race in Return of the Jedi) was sort of tiresome. The simpleminded puzzle plot reminded me of the last Tomb Raider film more than anything--both Raiders and Last Crusade did this better. So I differ with you in thinking the other films were better written, but perhaps that's just my faulty memory talking.

Partly, I'm just outgrowing my taste for mindless entertainment--or at least this sort of mindless entertainment. I had a similarly jaded reaction to that clip of Enthiran (the Kollywood action film heavily indebted to The Matrix). It was a lot of showy CGI with nothing to really pull me in.