It's a tale as old as time that developers, particularly junior developers, are convinced they could "slap together something in one weekend" that would replace expensive SAAS software and "just do the parts of it we actually use". Unfortunately, the same arguments against those devs regular-coding a bespoke replacement apply to them vibe-coding a bespoke replacement: management simply doesn't want to be responsible…
That's a great point about the management overhead of bespoke solutions. Often the goal isn't necessarily to replace the software, but to get a handle on the exploding costs of the 'expensive SAAS software' you mentioned. If you're looking for a way to manage and optimize those subscriptions without the 'weekend project' risk, you might find SaaS-Saver helpful. It's designed to help teams identify waste and optimize their spend automatically.