Several of the action sequences in "Last Crusade" left me cold, even the very first time I saw them.
The aforementioned speedboat chase in particular, especially the ending as the boat is being chopped up and Indy is fighting with Kazim. There is just NO real tension in that scene, the whole thing feels phony and forced.
The tank chase does have a few dull moments, but it's grown on me.
But LC has too many wildly implausible action beats. I generally like the motorcycle chase, but when Indy very limply tosses the flagpole into the spokes of the bike and then there is an EXPLOSION propelling the bike 20 feet into the air....eh, it's a bit much and would have been very easy to fix and make cool. Like maybe Indy JAMS it in the spokes instead of just casually tossing it there. And we lose the ridiculous SFX.
I also hate the "bag getting caught on the cannon" which is completely impossible and it magically gets uncaught the second Indy needs to climb back up and resume the fight.
Nitpicking, yeah, but those moments bug me slightly.
In general, Indy is far less vulnerable and fallible in LC as he is in the previous films, which is a shame.
In fairness, though, LC's action scenes are friggin' Jason Bourne compared to KotCS.