It's just +10 opinion; hardly a game-breaking loss. It's silly to demand that every game mechanic change be perfectly compensated based on the original game balance, especially when the mechanic change makes sense and has such a small effect on the game.
First of all, it is likely a game breaking loss for some small countries.
Secondly I do not demand every game mechanic be perfectly compensated. Thus your second statement was silly to the point of being absurd on the face of it.
Thirdly, if you think a 10 point swing in potential dipllo relations with another country is a minor difference then I doubt you have played the game very much and to the degree that you have played much at all, you likely do not play particularly challenging nations.
Absolutely nothing in your comment addressed the key point that making guaranteeing a matter of size further advantages the larger nations - the ones that some if not many of us find uninteresting - certainly after >2000 hours of eu4 I know I do.
So, if you're going to respond at least make a cogent comment that is relevant. Nothing that you wrote was.
And yes, making big nations even more advantaged over smaller is something they should compensate for because if the game becomes only about the big easy to play nations, it will very quickly become rather bland and unentertaining to play when you are tired of the easy nations and want to play the small and interesting ones and find that it's almost impossible to survive with many more of them due to more changes disadvantaging them.
The good news is that now that someone showed me how to use the ignore list, I shall apply it a second time.