A film's pacing has nothing to do with the age of the actors. That is a truly blatant misconception.
Certainly the latest movie's pacing is effected by a leading man who moves through it like a coiled spring. You can't realistically have a fast paced movie, with a low energy cast. It does
come across on screen.
Give credit where credit is due. I'm not the biggest fan of the two Abrams movies, but youthful Chris Pine brings an energy to his movie (not just his role in it) that neither aging Shatner or Stewart ever could.
... The Empath, The Paradise Syndrome ... Operation: Aniihilate! ...are examples of silly or stupid Trek writing.
Those particular examples do not match your description of them.