I got my parents in their 70s to use Ubuntu for a few years now. All they use is a web browser and word processing application for .docx files. They used MS Word for years and I found Only Office has a similar UI and opens word docs.
At one point I gave them an older laptop running windows again and they hated it. They wanted Linux back.
From my experience, OnlyOffice provides better compatability with MS Office-files (that is, more so than LibreOffice). However, having used Powerpoint quite a lot in my professional life, and using OnlyOffice Presentation to make a slide deck now, that is an area where I unfortunately find it severely lacking. There's also the issue about their license - I am not all that familiar with it, but apparently they are not as free and open as they claim to be.
I've never really liked the UI in LibreOffice either. It's usable, but always felt clunky to me. And it feels so heavy and ponderous to use. That says something from someone who wears the sackcloth and ashes of FreeCAD.......
I did use OnlyOffice for a bit and I thought it was better for my needs than LibreOffice. But it was still overkill my current needs. So now I'm down to just AbbyWord and Gnumeric since I only need the odd document and simple spreadsheet.
I can't actually find the View-menu (or any other of the usual File, Edit etc.). Maybe it doesn't play nice on KDE under Wayland? In LibreOffice Impress I can right click the gutter and click "More" and bring up what is called "Options - LibreOffice". Here I can find "Peronsalization" which allows me to select different themes (to no effect) and that's it.