The action sequences and set pieces were absolutely lackluster and downright boring despite the film's budget. (Not sure if this is due to the age of the actors - the John Wick series seems to have figured this out just fine.)
Most damning of all, the story arc, character arcs, and final resolution were phoned in and utterly forgettable. It's tragic, given the ludicrously audacious start of the film. The setup was there, but there was no investment beyond the trick premise.
Lana swung for the fences but struck out. It felt like an M. Night Shyamalan letdown.