Let’s agree to disagree. It’s true that these companies are vulnerable and lovely honeypots for hackers. And because they know that, they’ll try to harden as much as possible. Besides, not everyone is willing to create passwords out of algorithms seeded with mnemonics. Most of the people will reuse the same password over and over in different places. And that’s the worst situation, because most of those sites are hundreds of times more hackable than commercial password managers.
Are there better options than commercial password managers? Yes, of course. How many are willing to use them? Maybe less than 30% of the population. And that’s bad, because it makes the internet less safe for everyone.
And by the way, the method you use is one of the earliest ways to create passwords and is hackable by brute force in seconds. If I have two or more passwords, or two or more seeds, the algorithm is done unless you have some random generator in it.
Did you read my comment? I acknowledged that it is not something everyone will want to do. And you’re wrong, brute force methods won’t be able to break a 12 character password that’s random alphanumerics and symbols in any sort of timely manner. The only way they could retrieve the underlying algorithm is by successfully breaking multiple passwords and then cross referencing them to determine the code, which is extremely unlikely. By the time the brute force method found a solution, I would have changed the password already, as they all rotate monthly.