Picard has never been demoted
Captain Kirk has had like thirty titles and they always change and he goes from admiral back down to captain to something else entirely. He has been given raises and then demoted and it is all just a bit of a mess. But Picard has never been demoted.
Maybe it is because Picard is more level headed so when he gets a new position, he just accepts it and moves on to do his new duties. With Kirk, he constantly wants to be the star, in a lot of ways. He wants to be in charge and he wants people to listen to him so it makes him a little bit of a loose cannon. So no wonder he goes from having higher positions to being demoted.
With Picard, he has grown and knows what to do and how to get it done. He does what it necessary and it makes him someone easy to deal with. So he hasn’t been demoted because he doesn’t give people a reason to take away titles from him.
Picard is just better in general because he is easier to deal with than Kirk ends up being. Even in the new movies, Kirk is a thorn in everyone’s side.