My understanding was that the game was supposed to be about your dynasty. Thus getting titles under your dynasty was a success in and of itself regardless of if the title was under your rule. At least I felt that way when I was marrying off family and later having them gain a title some where far away.
I'm wondering if it was even intended that you be able to control the whole world personally. With threat level now it seems like they're trying to get it the way they intended. Have your dynasty be everywhere, but not you personally. They've said they went with external pressure rather than internal pressure to slow expansion because many would find it unpleasant if their realm just up and broke up leaving them with parts that might not have been their top choice.
I think your right about about paradox trying to recalibrate the game a bit.
Currently I don't think the games mechanics are quite deep enough to only worry about your dynasty. I feel the original game at release was another EU with Dynasties to role play with.
When designing the game Henrik admitted he tried to cater to the typical strategy game base. Strategy gamers are typically going to attempt to take over the world. It's second nature.
A quote from game designer Henrik
Fahraeus.
" I kind of chased some red herrings trying to cater to the old historical strategy game crowd. I should, in hindsight, have spent more time trying to develop the emergent narrative. If I could redo something, It would probably be that.”
Also dynasties were generally unable to control kingdoms and empires for hundreds of years yet the player can do it fairly easily. This is probably because it's game over as soon as you lose all your titles. There is nothing to do once you lose everything.
I'd love if they had went with internal mechanics instead of threat but I understand why they didn't. I think the forums would be even uglier if people's hundred hour ironman games ended because of new internal pressure mechanics.