I use Proton Pass for this. It creates the alias, which can be paused when not in use, and manages the login. The free tier gives you a handful but the paid tier is unlimited. If you own/buy a domain, you can configure it to be the domain for all of your aliases. For example, you walmart login could be
walmart@curious_dolphin.net



Cyberpunk as a literary genre, and the Cyberpunk TTRPG in specific, are incredibly prophetic. In the Cyberpunk TTRPG (which predates the WWW), "the net" is eventually condemned (as in boarded up) because of AI and ia replaced by silo'd networks (think extended intranets).