I think it's possible to flip the order. Instead of managing 100 passwords for each account, manage 100 emails and ONE password for all accounts. Make sure your password is really strong, and you should be better-off than managing those 100 passwords, which require a secure password manager.

Of course it's better to have a real password manager, but for most people, who don't or can't be bothered setting this up, this would be a huge step forward since they anyway use the same email and the same password everywhere.