I started experimenting with iCloud Keychain vs 1Password and came across this issue. Heck even with 1Password & Bitwarden this issue happens often enough to where my workflow was to create a record or change a password in the password manager FIRST...then just copy/paste it into the website.How about the many times you take the suggested password but then you do not get the prompt to actually save it and you are left with a new account which password you don’t know? SO annoying
That said, I found that if safari doesn't prompt to save the password, I can usually trigger the prompt by navigating to another page on the same webpage. If say I'm on the change password page, and don't get prompted... I'll click on the "home" or "settings" button on the site, which triggers a new page load and hence the safari prompt to save the password.