The issue is that password managers are a huge weak point and a significant compromise in your security. Generally password managers have some sort of master password, which unlocks access to
all of your other accounts. Why bother setting different passwords for every account if one password unlocks them all anyhow?
Password manager security flaws are also a dime a dozen, and none of them have been without significant flaws at some point or another. None of them are operated by companies with an ironclad reputation for security. And if you don't want to have a lot of issues going from computer to computer to phone, you more than likely will do what many password managers suggest, which is storing your password data in the cloud, which is even more laughable, because now we've secured all of your accounts with a single password, and then put the data that password unlocks out on the Internet where anyone can try to crack it.
Which is to say, if you really want to manage your passwords, don't use a password manager. Use a scrap of paper in your wallet, or a notebook, or a sticky note. Because all of those are vastly less attackable than a password manager, because they require physical access or physical proximity and probably the will and risk of accosting your person to get. Password managers, on the other hand, are somehow both the stupidest security idea we've ever come up with, and the thing that every "security expert" currently recommends ad nauseum. I don't understand it at all.
Now, sure, all those accounts you don't care about, if you want to randomize their passwords and store them in a password manager and say it's "better" than using a handful of common low security passwords, more power to you. I'm going to say you're wasting your time and effort (and probably money), but you're not hurting anything.
The problem is when you entrust that same password manager to your high security accounts like your email, your banking, etc. Accounts that deserve far more security than a single point of failure with some cloud app written by some company that doesn't do much else.