Paradox were already struggling to make popular European cultures and dynasties feel distinct within the limited scope of CK2.
They defacto gave up on that with CK3, and now that the map has been extended so much, there's no chance in Hell they're going to be able to give the various cultures, landmasses and kingdoms enough flavor to stand out.
And this is especially true with the glacial pace of content release of modern Paradox.
What is enough flavour? I play it like I'm the one creating the flavour with all the odd dynasties, cultures and nations I insert in to it. This might once again boil down to the point of CK3 being more of an RPG than a grand strategy game.
I'm trying to make Karelians the most badass people. Right now I have to kiss the ass of some Danish King-Emperor and serve as a little duke vassal in his glorious Empire of Scandinavia, but my bloodline is getting pretty fucking awesome.
One day our day will come. One day Karelians will be led to greatness by the notorious House Itkonen. One day they will all cower and tremble upon hearing our motto: Be Retarded
I've finally established a foothold for Judaism in Arabia after many years of mercenary work for the Basileus and his son. Started as a Hebrew culture adventurer of Rabbinic faith, short sighted as Hebrew is effectively a dead culture and has no technologies or land. The main drawback was no seige engines.
Made a new faith, an offshoot of Rabbinic called Judaism, with Chosen People, Divine Marriage and Communal Possessions. Made EVERYTHING legal, withcraft is virtous, unrestricted marriage, polygamist, theocratic head of faith, pluralist, the works. Family is also a witch coven and claims direct discendency from King David.
The Abbassids fractured a few times, it is now The Arabian Empire ruled under a Mashriqi boy who I've converted to our way and helped to stabilise the realm with my OP army of camels and Greeks. I've now purchased Gaza and settled as a vassal count, working my way toward restoring Jereusalem, taking the Empire and moving in to Egypt, hopefully maintaining strong alliance with Easten Rome in the process (Basil I's son is in charge and he's still my friend). Orthodox Christianity and Judaism becoming the 2 major religions instead of Catholocism and Islam, why not.
On succession, I'm going to establish another offshoot faith of Judaism that's the same but with Pursuit of Power, Divine Marriage and Sacred Murder. No head of faith and righteous instead of pluralist, all for the sake of expansion, Jewish assassins basically. "Mitnakshim" it will be called.