My password manager currently contains 714 entries. Memorizing is not an option.
The only memorizable passwords are the older ones, and those I have to manually enter on a nearly daily basis - and these are highly randomized strings that I memorized following keyboard patterns (and other tricks). My SSH key passphrase for example is a long sentence that I memorized. Everything else is randomly generated.
I also recommend that service:
https://haveibeenpwned.com/ . It's run by a Microsoft engineer, and it helps you getting warned when your email address is making the rounds on a new stolen password list.
Password managers are fine, as long you chose a good one, and you learn how to use it properly. The one I use allows me to sync passwords between multiple devices without relying on the cloud, and it has a feature that clears the clipboard once you exit it (in case you did a copy/paste of a password).