Regardless, this is a really cool project that further drives the point home. Props @sandipagr for a slick looking extension.
Me personally, I've just committed to ~5-10 minutes every week actually unsubscribing / marking spam every single email that doesn't belong and creating filters for the rest so they're neatly organized.
After literally 1 month of this commitment, I had a completely clean, inbox 0 about 90% of the time. Today every single email (with very few exceptions) that comes into my inbox is something I care about, or quickly ends up unsubscribed and I never see it again. Maintaining inbox 0 takes about 5 minutes / week.