Oh, absolutely. Cthulhu itself is very low on the totem pole, almost hilariously so for all its publicity. Literally a mini-boss, not even a Darth Vader to the Emperor.
I would give it a try. You can all see for yourselves if you like the changes, and you'll learn the new rules for any future 5.5 games you all might join in the next 8 years.
While I'm not the biggest fan of Cthulhu itself, it's nostalgic to see those old Cosmic Horror influences being rolled out again. I know it's corny, but there used to be so many stolen literary things just tossed into the game back then. :love:
Even if WotC gave Critical Role a giant thumbs up to use their IP for free, Critical Role is big enough it would rather not have to ask permission now or in the future. It's just easier this way, and we can all wink knowingly that it's Vecna.
And it even works great for WotC to just not say...
Heck, I blatantly include spells from earlier editions in my games, in ancient places forgotten by time. My players have found scrolls and even dessicated liches that throw around 2e spells!
This is even cromulent to settings like FR, where prior editions are just earlier periods of time, and...
I saw a funny version once. You spend an action to automatically hit and deal your weapon damage. No modifiers. It could be blocked by the Shield spell.
Magic missile in a sword, basically!