Is there a way to turn off Safari's strong password suggestions without also disabling autofill?

Select "Other Options..." from the dropdown menu. For example, you can create your own password, among other choices such as editing that suggested password, creating a password that's easier to type, or suggesting one with no special characters. Safari Autofill will be unaffected by whatever you choose.

FYI you are not addressing Apple on this site. The addition of those options in an earlier macOS release was the result of a suggestion I made to them years ago. So they do listen.

To contact Apple, Contact Apple.