What you wish to remove or add to linux kernel?

I was wondering what or how we can do to develop a better Linux kernel or variant (if necessary). What problems does Linux have and how could they be solved or if Linux needs some feature? **Justification:** Due to the system of usefulness of response, the great community that is here and the interest that can have in this response both to a passionate newcomer and to an expert. I think it is a question that could strongly favor the community, its development and the future of Linux development and variants.