I 'd like to point your attention to bad look of LibreOffice with dark themes. For example Breeze Dark.
Look at LibreOffice Writer. Icons are almost not visible. The other thing is ruler, also almost not visible. I'm not sure if this is theme problem or LibreOffice problem.

Screen from Kubuntu 15.10 daily build with plasma 5.
http://i.imgur.com/6LTQXcs.png

There is a bug reported for bad LibreOffice look with dark themes, but of "Importance: medium minor".
https://bugs.documentfoundation.org/show_bug.cgi?id=86617&redirected_from=fdo

Libreoffice is a multi-platform office suite which bundles a couple of icon sets into the application. And to not overdoing only the default Breeze was added. However, it is planned to adjust the color of the icon depending on background. To make sure that devs will not forget this issue I filed a bug report https://bugs.documentfoundation.org/sho ... i?id=91322

Heiko Tietze wrote:Libreoffice is a multi-platform office suite which bundles a couple of icon sets into the application. And to not overdoing only the default Breeze was added. However, it is planned to adjust the color of the icon depending on background. To make sure that devs will not forget this issue I filed a bug report https://bugs.documentfoundation.org/sho ... i?id=91322

It's 2019 and LibreOffice still looks terrible in KDE Plasma Breeze Dark. It's toolbar icons are too dark and very difficult to see. I also followed your bug report link and ended up at a 404. This isn't good at all.

It is a very old post. Now LibreOffice can look quite good. Now I use Colibre icon style.

https://i.imgur.com/lwCNc5Y.png

For general look I use VCL: KDE5

https://i.imgur.com/0MJ8jyD.png

https://wiki.archlinux.org/index.php/LibreOffice#Theme