Dedicate a full day to the following:

1. Buy a domain that looks like a knock-off email provider (to avoid some scrutiny later). Something like emailco.biz, etc.

2. Setup simplelogin for that domain.

3. Go through all your existing accounts and change the email to [service]@emailco.biz.

4. Use that technique to sign up for all future services. If you start getting unwanted email to a simpelogin alias, simply turn it off in the app or browser extension.

5. Click unsubscribe on every email you don't want. The first day it will be a lot, the second day less, the third day even less, etc.

6. Ruthlessly click spam on anything you didn't ask for.

Soon, you'll have it under control.