A lot of websites use complex login forms that make it harder to use a password manager to sign up, login and update credentials. It would be very helpful to show that somewhere and create pressure for better compatibility across the web. Password managers are becoming ubiquitous and they need to start being more transparent and not a hassle to work with.
This could be done as a database of scores maintained by Lastpass or a dynamic check on the entry URL that can be performed by the Lastpass client upon request.