Things disappearing with insufficient explicit feedback for what actually happened to the things is one of the most common issues I've encountered with older computer users. I think it's the most common issue. Toasts add persistency and visibility for users who barely or don't understand the UIs they're interacting with, which makes it easier to understand what happened.
If Outlook gave feedback to every user action in a toast, then provided a universal history of every toast, you would probably resolve a significant amount of issues caused by user actions leading to unintended changes (and being unable to recognize that the action lead to a particular change, or even how the current state differs from the previous one).
The whole point is that they DON'T add visbility, because they're not presented where the user is working. Age isn't even a factor.
It's time to stop blaming "age" when the more likely explanation is EXPERIENCE. Many people learned to use computers in an age of well-understood GUIs that hewed to standards that evolved for very good reasons. For example, buttons that were depicted (in a clean, not cheesy "skeuomorphic") manner. You can tell at a glance if a well-depicted button is on, off, or disabled.
Then enter the idiotic "flat" design fad, where the entire screen was an Advent calendar of no controls at all... or is it ALL controls? Click on every piece of text and every rectangle to look for the hidden goodies.
Those conversant in (and tolerant of) more-recent UI have simply become accustomed to shitty UI. They've either forgotten how bad it is, or grew up not having experienced good design. Another great example that has disappeared in many areas is GREYING STUFF OUT. If something is not currently usable because it's not applicable, you don't just make it disappear. You grey it out, so users can learn
1. That the function exists
2. Where the function resides
3. What conditions must be satisfied to make it work
Things disappearing with insufficient explicit feedback for what actually happened to the things is one of the most common issues I've encountered with older computer users. I think it's the most common issue. Toasts add persistency and visibility for users who barely or don't understand the UIs they're interacting with, which makes it easier to understand what happened.
If Outlook gave feedback to every user action in a toast, then provided a universal history of every toast, you would probably resolve a significant amount of issues caused by user actions leading to unintended changes (and being unable to recognize that the action lead to a particular change, or even how the current state differs from the previous one).