I don't think password manager's could be trusted enough to generate a password for use, mostly when it has to be used for some thing very important or financial stuff.
Password managers are open source software used by millions of people. If you don't trust them, you might as well stop trusting all Bitcoin clients, all operating systems, all hardware, all algorithms.
People who misunderstand security tend to weaken themselves by focusing on the wrong things and trying to reinvent the wheel, while lacking the theoretical knowledge to do so.