How to find myself with a partner who is refusing work on growth?

I (27F) have been in a relationship for the last 5 years. I have come to the conclusion that he (30m) is does not want to grow as a person yet. I’ve been waiting for him to but I haven’t seen anything. Because of this I feel like I am also not growing as a person so I’m looking for advice on how to grow as a person within an unfulfilling relationship? I am not in the position to break up with him yet. ( I know I should and I’m working on it mentally) but until then what can I do to help myself growth within a relationship? I am starting to take myself out on “dates” more but I have pretty bad social anxiety and it can be scary for me to do things alone. He is rarely home. Always with his friends so I have been hanging out with myself more. And I just want to continue to grow in other ways while stuck in some.

TLDR: how do I grow in a relationship that is unfulfilling?