It starts with things like fixed-with fonts in the presentation. Great for code, really annoying for long texts. There are enough editors that still do some correction passes on paper, because it works better than spell-checking hundreds of pages on a screen.

I don't think many people are particularly attached to Word, it is just the most common thing that does what they expect. But similarly, tools would probably need at least some WYSIWYG-features. Like a simplified Word, with more sensible back-end formats and the ability to do diffs and merges also in this mode (similar to the change-tracking features in Word). If it is professionally published, complex layouting is done in different tools like Adobe InDesign anyways, so it doesn't need to be able to do much in the way of that.