Please understand, ink and space is limited when a book is put together. Paizo has to choose carefully what they put in as apposed to data overload. As a player, the reason I bought the Bestiary 5 is the monstrous humanoids, humanoids and undead.
Those are the beasties I can turn into and keep my armor, sword and the like when I change shape. Polymorph is like gas on a camp fire in a fight. Getting larger and having multiple arms creates options. You can carry a reach weapon and a melee weapon to threaten all squares you threaten. For changing shape to a larger creature, increasing to a size large creature gives a +1 to attack with CMB against CMD unlike a -2 to attack AC. For turning into a size Huge creature, a +2 is given to attack CMD with CMB. Sunder, Trip, Grapple, Reposition and the like are incredibly successful on low rolls. Not to mention the damage output increases along with reach in which creatures smaller than you can not take a free shot if they can not reach you when you provoke.
I like the layout of the book, the stats of the monsters fulfill roles that the other bestiary's do not completely fulfill. As a GM, ever since the first bestiary, the monsters are scarier and scarier as each Bestiary has come out. That means as a player or a GM, the fire power can be increased for the players and more fire power means more epic fights.
As a side note, I feel the story should propel the fights just like it should propel the role-playing, investigating or what not. I have noticed players like fire power. The more people play the more fire power the would like to have. Such increases means greater rules struggle. The more I play and understand chapter 8 of the core rule book, the more the rules become easier and that struggle has become less.
