At that point, just get a custom domain with a catch-all email system. Any emails sent to the @[domain] address will hit your inbox, so you can do things like Target@[domain] and Walmart@[domain]. Then if you start getting spam from one of those, you know who leaked it and you can filter them into spam. All without needing to go through the hassle of creating a new email address.
Hell, my password generator (Bitwarden) even has the option to create custom usernames for a catch-all system. It can either do them randomly (like the passwords) or pull them from whatever site I’m making the account on. So like it’ll pull the site’s title and use that as the e-mail address, then append the @[domain] to the end automatically.