Safari stopped auto-filling saved password data, any 'fix'?
This is only a partial answer covering a slight alleviation for:


  Yet another marvellous new 'feature' - Safari 11.1 now will not auto-fill any login data unless you specifically click the first field, select the login drop menu, select the login…


My personal grievance with this situation is that there seems no way to use the keyboard for this and being forced to use the mouse/trackpad to hit a usually tiny caret to achieve the desired result. Using the keyboard for this task would be at least much faster and less error prone. 

Unfortunately, it looks as if you still may use Tab to get to the username field, but after that all keyboard actions seem to be inert and it's back to using a pointing device?

That seems to be amplified by a bug. If you Tab past the username field and into the password field, then Shift+Tab back into the username field, then the information is auto-filled in for the most recent credentials and you may even select other identities with the cursor keys.

This behaviour differs depending on the page in question and also has its level of practicality depending on the page design: how many fields there are to tab into, before reaching the desired one.

On a relatively cleanly designed page like Apple's developer program login page the behaviour is as described above. On other pages the behaviour can sometimes be different and even be more like it was before. For example, Microsoft dedicated login pages preselect an open field and it's just a cursor down + Return to go forward.

This was tested on 10.12.6 and with Safari Version 11.1.1 (12605.2.1).