From the blog post:
“We’ve also gotten strict about which monsters get the Humanoid creature type. This type is now reserved for creatures who are humanlike in their moral and cultural range. As we update older books, we’ll reassign some Humanoids to other creature types. When Monsters of the Multiverse is released, you’ll see that some former Humanoids are now Monstrosities, Fey, and other types.”
I’m not sure what “humanlike in their moral and cultural range” means exactly, but I wish he was a little clearer what goal is served here that makes it worth myriad arguments about whether a Charm Person spell works on X creature that players expect it to work on. At the moment when a player needs to guess if a creature is a humanoid for the purposes of a spell or ability they basically have to consider whether it is a tool and equipment using biped native to the material plane and of non-giganitic purportions, now they also need to consider it’s species’ “moral range”.
I would find it easier to get on board with the change if Jeremy Crawford had taken the opportunity to state the actual reason WotC considers this change worthwhile. I don’t think it’s inherently a bad thing, I just think it’s something they shouldn’t tinker with when the spells and abilities in the game were written with the assumption that being humanoid was synonymous with personhood. If in the next edition they want to hand out a separate “person” tag and have spells and abilities cue off of that I think construing “humanoid” as the narrow group of mammilian bipeds or whatever they wanted to confine it to would make a lot more sense.