Alternative: Run your own server so that you can have as many mailboxes/aliases as you want. Give each webiste, company, or even person a different alias. The moment you receive spam, revoke the alias, and optionally name and shame spammers.
Some email providers and postfix also allow the creation of dynamic aliases of the form user+alias@example.com.
One thing I noticed is that most mailing lists now have a header that identifies them with a specific ID. When I click "Make rule from this email" in Fastmail the primary option is to sort it by that header, not by the sender or receiver. That way only the marketing emails get redirected and not transactional ones from the same sender.
List-Id: A Structured Field and Namespace for the Identification of Mailing Lists
Some providers simply straight up refuse +ed aliases. I really like how gmail breaks RFC by using dots at any arbitrary position of your username. This is not at all an efficient and correct use of aliases but it gets the job done sometimes
> I really like how gmail breaks RFC by using dots at any arbitrary position of your username.
Do they? I think the local part can be anything that the MDA chooses to accept and that different local parts of an address result in the email message being placed into the same mailbox, is nothing an RFC would forbid.
A reasonable alternative, if you value deliverability and don't want the actual hassle of maintaining a mail server, choose a mail provider, like mailbox.org, that allows bringing your own domain.
Some email providers and postfix also allow the creation of dynamic aliases of the form user+alias@example.com.