There was a thread I remember called favorite skin 2021 or something like that ( but I can’t find it sadly) where people were discussing their favorite skins to use on their vero 4ks
Plex itself doesn’t have official support for skins so their plugin looks and works similar to their web interface and various apps on other platforms. If you wanted to change this the easiest way would be to use the PlexKodiConnect add-on which instead of being a separate library that is run from the add-on, it does some magic to add and sync your Plex server into the regular Kodi library. Once you have that then you can switch Kodi itself to a different skin.
You don’t have to uninstall the Plex add-on. It is not needed, but it doesn’t hurt anything. For more information including how to install see its thread on the Kodi forum…