Libreoffices UI is DIFFERENT to Microsoft Office.

Thats the real impediment. I have applied "make it more like that" changes including font uploads. It's good. But it doesn't get over the user "principle of least astonishment" which is what drives the resistance.

There is a similar problem with the UI differences on OSX. otherwise rational people find the experience of moving to Office on OSX too hard.

(happy MS Office user on OSX, tolerably happy Libreoffice user on OSX and other platforms)

I don't know what it's like using modern Microsoft Office with no experience using toolbars and menus and then switching to LibreOffice, which still uses traditional toolbars and menus.

I prefer traditional toolbars and menus, but I remember Microsoft doing user studies when developing the original Office 2007 ribbon. It showed that the ribbon was more productive for beginners and casual users. Given that many office suite users are casual users who use word processors, spreadsheets, and presentation tools, Microsoft Office may be more productive for them than LibreOffice. It would be good if LibreOffice did user studies.