As a developer you should support a proper form that works with password managers. Period. Anything else is a failure on the developer's part to create a working login. It's also a massive security hole you've introduced by encouraging people not to use password managers. They will try to remember the password and we all know where that leads to. Sorry, if you think you can develop a login form that doesn't support password managers and call that a decent effort, you're badly mistaken. That's just shit engineering.