What makes a great story producer?

I've been working as a researcher/producer for years and want to shift to creative, helping to shape stories instead of focusing so much on execution in the field. Done plenty of writing but I have no SP credits and I've found my varied experience is not always valued. Do great SPs have a writing degree? Expertise in one format, field, or network? Longevity with a company? Writing spec scripts to show in a portfolio of potential... is that done?