There always will be what to do and improve. The main function makes the most influence on what you want and do - as it's the main content of the consciousness.
While the main "source for personal evolution" are weak functions. You can improve yourself there in the most degree, as those functions stay at child level below social norms. Get love with a dual - and this process may go well. There was a little discussion.
Sure, you may improve some _skills_ in strong regions, but this will not change you much as a whole person, will not give such satisfaction and self-esteem, will not make your life so much better and felt fuller.
I don't agree with your interpretation, I believe the creative function is generally the main source of personal improvement and personal impact on the world (I'm not the only one, there's quite a lot of consensus on this). It's not like we are going to find an agreement on this, we can stop this debate now, ok?
Or perhaps you kind of misunderstand some of the terms I'm using, by personal evolution I mean personal "fulfillment", not "balancing out all your negative aspects".
Obsequium amicos, veritas odium parit