How do I enable automatic password entry on my iPhone?

So I'm trying to understand why my iPhone (iOS 18.3.1) won't automatically enter usernames and passwords for login requests. If I go to Setting>Apps>Passwords>Open Passwords, and select the app requesting the passwords, the usernames and passwords are right there. But when I try to log in, it asks "Enter password", and I have to type it in manually. I CAN press it and request AutoFill, and select Passwords, wherin I'm taken to the "AutoFill Password" list. I can access the password there, press on it, and it will fill it in, whereby I can connect. BUT THAT'S NOT AUTO-FILL. It's manual fill, in that I have to manually tell it where to get the password.

I should say that in "Touch ID & Passcode", "Password AutoFill" is turned on.

I want to open the app, and have it automatically fill in my password, maybe after Touch ID.  Boom! It's done. How do I make that happen? At one point in the past, when I was asked to "Enter password", it would specifically ask me where I wanted to get it. From Google, from my browser, or wherever. That was inconvenient, but workable. But it doesn't even do that anymore.

The system knows all my passwords. Why can't it just drop them in for me?

This is really annoying.

[Re-Titled by Moderator]