Agreed.

IMO a toast showing up shouldn't be a direct/immediate response to user action at all, ever. Toasts are purposely designed to steal attention. Don't try to steal attention from the user performing an action just to confirm that the action occurred; you already had their attention!

> if it's important enough, why not show it as a persistent alert on the page itself?

Because it's a crutch against bad design in an era when many companies don't employ designers, or arguably even as an exploit to be leveraged by marketing to try to brute-force the conversion of users to sales.

While there's nothing inherently wrong with them, I've become so accustomed to toasts being misused/abused that my instinctual response to that visual stimuli is that it's focus-friction and tantamount to being spammed, even when they're being used in benign or debateably useful ways.