Once again I don't get the downvoting. You're right. I'd love nomads, republics etc. to be added. I am sure they will at some point.
Some people don't seem to understand the meaning of the word fundament. CK3 is not a burning heap of absolute trash. I wouldn't even call it a bad game per se. The fundamental mechanics behind it, however - its main structure - are the problem and the main reason behind this thread. Like you mentioned, stacking bonuses upon bonuses is an issue and so is playing the game the way the tooltips tell you to - even when roleplaying hard as others have mentioned earlier - because the AI seemingly doesn't appear able to read them.
You can add content to your heart's desire - and a lot of it is good - but the essential foundation behind the game has not changed and if it will not change, I consider the entire project a failure.
Even describing CK3 has having fundamental structural problems isn't quite conveying just how deep the problem is. It is possible for a game to have major structural problems but still retain some hope of fixability. But I think that CK3's design problems are sadly outside of that realm. In short, they are worse than being fundamental in nature. They are
fundamentally unfixable.
For instance, I simply see no way to ever endow AI characters with any semblance of coherent behavior when the game
1) has absolutely no mechanism to model an AI character's long-term goals or strategy,
2) instead uses random events as triggers to dictate character behavior,
3) builds 4+ years of DLC content over the premise that characters are nothing but blank slates for event triggers.
Random events can never produce coherent character behavior any more than some very primitive random word generator could produce a coherent story. And game designers who somehow think they can "fix" this problem by tinkering with the random generator to make certain words more likely have such spectacularly poor judgment that I cannot take seriously anything else they say.
At this point, this problem is completely baked in. All DLC events are based on it. Fixing it would entail not just putting a better fundamental structure in place. It would amount to throwing out the majority of the content added in CK3's lifetime, or reworking each and every individual piece so radically that the result would be not so much "fixing CK3" as it is "as cannibalizing the art/text of CK3 to create a new game and calling that CK3". At that point, it would probably be less labor to simply declare that you are making a new CK from scratch and recycling art/text from CK3.
As for whether the game qualifies as being a burning heap of absolute trash. Well, that depends on how you define "a burning heap of absolute trash". I personally couldn't think of a more appropriate definition than a game being fundamentally unfixable.
So why are we here? Well, I am here because I believe the fundamental flaws of CK3 need to be carefully recorded so that future endeavors don't make the same mistakes.
That said, I want a different dev team for CK4. The deepest underlying cause behind the failures of CK3 is not bad structural design. Lurking beneath that is poor human judgement.