The Last Sharknado is simply a collection of images and noises loosely cobbled together in a way that somehow makes them barely suitable for ironic viewing.
It's clear during [the climax] sequence that we've gone well past the point of Peak Absurdity, as far as potential humor is concerned, and the big climax thus leaves the viewer cold.
Aside from sheer exhaustion at the overwhelming set pieces & shark puns, Fin and April and Nova did become endearing characters. They deserve the same kind of sendoff Rocky Balboa, Freddy Krueger, Jason Voorhees, Jigsaw and Ellen Ripley got!
Honestly, The Last Sharknado isn't bad enough to be good and isn't good enough to be good. It's kind of just... there, lacking the gore of splatterpunk and the sanitation of kiddie-fare.