Another group of friends started Personably from exactly the same strategy - we had a script to create dozens of calendar invites for new joiners with all their onboarding details, so things didn't get missed.
Dependabot has ~100 paying customers, and makes just over $2,000 a month. It's still quite a lot of work adding new features, but if I wasn't extending it's functionality it would be passive income.
Personably have raised money and landed some big paying customers - I think there's scope for them to be solving a relatively large problem, having started from a duct-tape fix.
The only proviso I'd add to the article is that sometimes the problems you find like this are small. Dependabot will never be a full-blown startup - it's scope is too small. That's not necessarily a bad thing, though - I think the problem has still been well worth solving thoroughly.