There are a lot of quality of life improvements in ck3 and a few new fun mechanics, but overall it's way too easy and lacking in flavor or immersion. Once you've played one country, you've played them all.
It's good! It depends on what you liked about 2 though, since they did shift a lot of the points of focus for 3. I personally like that they leaned into the roleplaying aspect of it. Managing a large realm is now a much more active task than it was in 2. It's a shame that stuff like nomads and merchant republics aren't playable yet, but I do think that the feudal gameplay is substantially better.
I played shortly after release and felt like I ended up spending more time on genetics and bloodline manipulation rather than ruling countries and politics, because making superhumans felt like it had more gameplay impact than anything else. Has that changed much?