We just got back a student F31 SS and I was heavily criticized for (still) not having enough mentorship experience. True that I have only graduated 1 student so far. That student had an NRSA and is now a PD at MIT. They are still asking for a senior co-mentor. Is this valid?

At what point in our careers do we not get this critique?! What are the underlying reasons from senior faculty that make them so worried about this? I'm otherwise well funded and this work stems from discoveries made in my lab! #AcademicChatter