Getting error: Too many categories: There are already 500 categories; importing 1 more, would result in more than 500 categories (the upper limit as of now)

Yea those notifications would be important. And because they're more important than regular notifications, I would argue you should be able to provide a special email address to receive those kinds of notifications/warnings.
In the same way you might have a separate billing email (to receive invoices) or a security-update email.

In any event, getting important notifications like that on a special email would allow us to filter them and react accordingly. Maybe you could have notifications/emails sent for when something reaches 50% of a limit, then again for 90%.