I dunno, it mostly seems to not work when companies change their field names/IDs, or just 3rd party authentication, then you need to manually add domains. Otherwise my password manager (1Password) works everywhere where I have an account, except my previous bank which was stuck in the 90s and disallowed pasting the passwords. If you find that your password manager doesn't work with most websites (since it's "extremely common") you might want to look into a different one, even Firefox+Linux combo works extremely well with 1Password. Not affiliated, just a happy years+ user.
> Passkeys seem like the best solution here where you physically can not fall for a phishing attack.
Yeah, I've looked into Passkeys but without any migration strategy or import/export support (WIP last time I looked into it), it's not really an alternative just yet, at least for me personally. I have to be 100% sure I can move things when the time ultimately comes for that.