You shape-shift into another creature for the duration or until you take a Magic action to shape-shift into a different eligible form. The new form must be of a creature that has a Challenge Rating no higher than your level or Challenge Rating. You must have seen the sort of creature before, and it can’t be a Construct or an Undead.
When you shape-shift, you gain a number of Temporary Hit Points equal to the Hit Points of the form. The spell ends early if you have no Temporary Hit Points left.
Your game statistics are replaced by the stat block of the chosen form, but you retain your creature type; alignment; personality; Intelligence, Wisdom, and Charisma scores; Hit Points; Hit Point Dice; proficiencies; and ability to communicate. If you have the Spellcasting feature, you retain it too.
Upon shape-shifting, you determine whether your equipment drops to the ground or changes in size and shape to fit the new form while you’re in it.
* - (a jade circlet worth 1,500+ GP)
So we use the entire stat block for the new form except for the hit points now? Why is this better?
You get temporary hit points equal to the hit points of the new form. Once those are gone you change back. I'm not sure why the change. Maybe so you can't heal your shape and stay in it longer?
This is OP infinite HP. when you shape-shift doesn't that when you cast the spell. so you can shape-shift as an action as a new beast. turn from a bloodied pit fiend into a full temp hp brass dragon and you're temp hp is restored way different than old shapechange