This movie was going to flop with or without Kennedy... yes she made it worse, but no one was clammering for another Indian Jones movie, no one.
Crystal Skull destroyed the franchise, betrayed the fans, and there was not a chance in hell a new movie was going to draw enough ticket sales to make money
With a $300 Million production budget, and likely more than that on promotion, this film would need to see over a BILLION dollars world world wide to be profitable and it that was NEVER going to happen.
And for the longest time Ford kept saying he didn’t want to do another Indy, or Star Wars for that matter.