* If 1 to N password(s) leak the pattern may be obvious leading to your other accounts being compromised
* Not all sites have the same password “rules” so there is no algorithm that works for all passwords without you being aware of the rules of the given site. Rules that only you only (may) have access to at signup time.
* Typing passwords out manually sucks (slow and error prone)
1) only matters if you're a very high value target who is being manually target. Doesn't apply to 99.999% of people, who only need to worry about credential stuffing and brute force.
2) Similarly, it's not hard to come up with an algorithm that satisfies 99.9% of websites.
3) To a lot of people, managing a password manager sucks.
I personally do use a password manager and automatically generated passwords, but also understand that for many people it's the better option.
Dedicated 2FA on a hardware device seems pretty resilient, I hope more banks incorporate it instead of SMS 2FA. Hosting vaultwarden also seems pretty good because it’s unlikely for you to be targeted, but requires selfhost maintenance.