The eleventh film in the franchise isn't that far removed in tone from the fifth at times.
True, which is one reason why I didn't like JJ Trek. However, the audience's perception of humor has changed. Look at how many people enjoy watching skateboard wipeouts on Youtube. Also, the humor within the context of actors in their 50s and 60s is different from humor within the context of 20-somethings. Slapstick is really better with young actors.
For instance, when Scotty hits his head on the beam in Trek V, it makes people take him even less seriously as a senior officer than they would because of Doohan's advanced age and portly physique. It destroys your suspension of disbelief and makes you think you're watching a Naked Gun movie. When Simon Pegg does his Willy Wonka trip through the tubes, people accept it more because he is young and hip and it's all in good fun. For some reason it doesn't pull people out of the world the way you think it should. It does for me, because I'm a Trek Snob(TM), but not for mainstream audiences.
The TOS cast were criticized for being too old to cut the mustard all the way back to TMP. You have to be very very careful how you inject humor. It was done tastefully in Trek IV, but not tastefully enough in Trek V. The audience started laughing AT the cast instead of with them.
Trek V feels like a cast reunion in which the actors rarely ever truly appear "in-character", which was, I think, Shatner's doing. He made them act in a very casual way, which made them more personable, which was good, but also less believable as senior officers in positions of respect and high-authority, and this was directly opposed to what the franchise had set in motion with the stiff TMP and the sweet spot of Khan where Kirk is the seasoned pro with occasional bouts of winking and rule-breaking.