There does seem to be a gap. The only beast above CR 5 I could find of that size was from Descent into Avernus, the Traxigor:I'm just hoping we'll see some beasts in the future that are CR above 6 that don't have to be Huge or larger in size - something that will fit in a dungeon and is something other than the T-Rex or Giant Ape for high-level polymorph/wild shaping.
according to the Wiki that is a polymorphed Archmage, so not really a beastVery odd creature for a beast with its spell-casting and high intelligence. Not sure how this even qualifies as a beast.
your sarcasm is deliciously dripping...Just what we need, another aspect of MOAR POWER!!!! MWAHAHAHAHA!!!
So, D&D takes yet another turn for becoming Superheroes vs. God-like monsters. Wonderful...
They should change the name for the next edition: Demi-gods and Destructors.