They clarify that the Aberration creature type means that the monsters are unnatural creatures specifically from or linked to the Far Realm. So, Kuo Toa, Grimlocks, Gith, Piercers/Ropers, and more are now Aberrations. Slaad will presumably have some lore connection to the Far Realm now.
No stat blocks were presented IIRC. They mentioned new stat blocks (Githyanki Dracomancer, Kuo Toa, Blob of Annihilation, etc). There was a lot of new art.
They mentioned that if they were completely redesigning the game they would probably remove the Ooze as a separate creature type and fold them into the other creature types such as Aberrations, Monstrosities, and Undead.
The only Humanoid monster stat blocks are in the NPC section, so old Humanoid monsters are either moved to a different creature type (Gith, Grimlocks, and Kuo Toa to Aberration, Goblinoids to Fey, etc) or are being absorbed into the NPC stat block section of the MM (Orcs).