PlasmaTube doesn't seem to be created with the same framework used to create Plasma fast apps like Dolphin, Kate... the transitions, animations, clicks feel really slow.
This has nothing to do with PlasmaTube itself, if all QtQuick applications (which is the framework used to create PlasmaTube) then there might be an underlying system issue like graphics drivers. Please open a thread on KDE Discuss if you need further help with that, but it's nothing specific to PlasmaTube here.