Some things I did during recovery which feel related, though I make no hard claims:

• regular talk therapy including about those issues
• be completely genuine with at least one person
• change employers
• mentor an intern
• work with a team who were all selected to be both high-functioning and low-ego
• learn about imposter syndrome
• accept that I was depressed to the point that I lost a number of years of experience ("explain away" a certain portion of the feeling as genuine)
• work with an individual who I felt was competent but who I was distinctly more competent than in select areas
• complete a substantial at-home coding project

It is entirely possible that recovery was simply regression to the mean. I do not know.