> Toasts are also not accessible for folks with low vision

To make this a little more concrete with one example: if you are using fullscreen magnification, odds are toasts will literally never appear on your monitor. By the time you pan over to their little corner of the screen (if you ever do), the toast will be long gone.

Can confirm. I zoom and pan on lots of websites in my daily browsing and would have no idea if toasts are popping in and out. I'll notice system level toasts though.