Sometimes this game delivers by making things look rough and messy for while, until things turn out good in the end, if you just hang on. I had game where I had 3 male heirs and decided to disinherit 2 older ones, so my realm wouldn't split up, and when my King was near his death, I realized that heir I had chosen was fucking gay.
This freaked me out, I was like is this minor mistake going to cost my successful run so far going from small county to kingdom, just get fucked cos of one fag ruined all of it. Luckily despite being gay, he actually had 3 children with his wife like what the hell, and only 1 of them was male, so things suddenly looked bright again, until this heir started having intimate relationship with his mother, and it became public knowledge. And that and other reasons made his early reign pretty hectic.
Fortunately from these two disasters came my best ruler yet, and there haven't been better since. Extremely high stats on learning (which is what I really wanted), genius genes, great wife and lived very long. Loved by all vassals, and pope himself was sending checks nonstop. I had planned to little by little taking over area of France to make into Empire, but suddenly opportunity of conquering kingdom of Corsica became option out of nowhere, which I couldn't resist.
Then I was fairly close having Empire in Italy instead + those large territories in France. Unfortunately this perfect king couldn't be there to establish that Empire, cos I had to spend money helping allies in their wars, because of I was trying to be nice to allies. In the end, king Abraham II of Brittany couldn't finish what he started only, because of Byzantine and East Francia couldn't stop fighting other realms
The end.
Side note, when CK3 came out I was focusing on stewardship stat, cos I thought money and direct control of as many as possible counties was way to go. It was really good and amount of money made things little bit too easy sometimes. But this time, I decided to try Learning, which turned out to be really nice too. Celibate perk was excellent skill to manage how many possible heirs you have, turned out to be quite handy. Then you add fact that you can longer which is big plus too, and marrying someone really young (or postpone marrying completely) so that you can make male heir far into reign so they can also hold power for very long time is another win for Learning