CK3 sucks absolute ass. The 3d characters are kinda neat and innovative, but that's about it. The map is a combination of Imperator Rome's updated clausewitz engine combined with EU4, I dislike it compared to CK2's map. The paper map on a table is dumb. They've locked the console window behind the debug menu, and its typically still inaccessible even when debug mode is enable in my experience--this is a bug from Imperator Rome they didn't bother addressing and there is significant outrage over it on paradox plaza. They've stripped out many CK2 features such as societies, the college of cardinals, trade routes, and more. They'll probably be offering these as DLC in the feature which is scummy as fuck. The UI and familial parts of the game have been significantly dumbed down, both of which were renowned parts of CK2.
Also, as someone mentioned, they've only added two starting dates: viking era and 1066. You can't play as the plantagenets, you can't play during a specific Crusade or Jihad, etc. But hey, on the upside, you can start the game as a black female child ruler in africa (who is probably queer to round it off).
I expect they're facing financial pressure due to Imperator Rome being a complete flop and rushed CK3 out.
Zero, asides from Crusades being a thing. There is no mention of Deus Vult. In fact, Paradox has proactively banned the use of Deus Vult and Pepe the Frog on their official discords. I joined the CK3 discord to get some help and before I could even read their rules I was muted and kicked for having a Pepe in a Hazmat suit avatar. Nordcucks are real.