You could use one email for everything or you could use a combination of different email services for different purposes.
Try these alternatives:
iCloud Mail for account logins, mailing list subscriptions, etc
ProtonMail for when you actually need to email a human. ProtonMail is super secure, which you can use with a custom domain if you want or it has a free account with decent enough limits to help encourage you to declutter your mail.
Maildrop for when you need a 100% disposable email address. All email addresses are public so you don't want to use this for anything important or secure. This comes in handy when registering for “free” WiFi access in coffee shops and on the train. Remember: free means free. Exchanging your data for Wifi is not free.