The rocket sled isn't a problem and the aliens aren't too bad until they get up and walk around. We never actually saw a "God" in the previous 3 movies. Just the power of it.
They should have ended the opening sequence with the rocket sled. That was bombastic enough, nuke town ruined it and also drags it out way too long. It'd have also made more sense to cut back to the college and have Indy surprised the FBI searched his office. In the movie as it is, it makes no sense that he's shocked by that considering he was already in their custody and being questioned.
The real problem becomes Marion's horrible acting and Mutt's over the top nonsense with monkies and getting hit in the balls multiple times. The villains also don't hold a candle to the old school ones. They missed an opportunity to make them more menacing by showing them actually massacring the Ugha tribe.
There's a good movie in there but weighted down by George and Steve's recent inability to show restraint.