For me it is stronger that Kaladin didn't swear the Fourth Ideal than if he did. I wanted it so much, but it is just so human. Even if he knows these words he isn't ready to say it. There is a difference between knowing something and accepting it.
He lost so many people he cared about. He have to deal with it. To accept it. To forgive himself. It's like Lirin said - You can't protect everyone, you have to let it go. For every surgeon or any other physician it is very important to learn that people die. That you can't save everyone. And I think that Kaladin refuses to admit that Lirin was right.
And those who he lost - of course he could just swear Fourth Ideal but what about grief? If you lost someone in real life time is needed to cure you. Even if someone tells you - it's time to deal with it - maybe sometimes it helps, but most of the time it won't work. Sometimes little things will make difference - like just that someone is near you someone that you could count on like Bridge Four for Kaladin. And sometimes it is better when you lose than when you win like when he can't swear the Fourh Ideal.
And there is this thing that Kaladin said to Theft when he swore Third Ideal - That it won't make any difference, that it won't solve all problems. That you have to deal with your dark side anyway.
I don't think he didn't grow in Oathbirnger - he knows that he can rely on other people, that he isn't alone any more, that he can make mistakes, that even if he won't make right choices it could end well anyway. And that makes him stronger. And maybe he could deal with his problems and make decisions.