Looks like software from the 2000's :( They should just hire someone to make a modern design
Something like LibreOffice is a giant piece of software produced by a team that is far too small. They have to be conservative, and they have to focus their energy properly.
Frankly, instead of playing around with trying to make things "beautiful" (which is hopeless anyway, given how opinions differ), I'd rather they turned their design brains towards the kind of small tweaks that make the UI flow better. There are bound to be hundreds or thousands of little corners where twiddling slightly with the layout of menus, dialog boxes, etc. would make users more productive. Focus on those, please. (Note that judging by the more detailed reports, this is actually what they are doing.)