@Genstar I had issues changing the theme on Elementary OS. Then I installed Kubuntu and it worked perfectly. Go figure. :/
You can in System Settings -> Apparence -> Color and with Plasma 5.17 this should also work with gtk3 applications
@carl The changes I would make there wouldn't affect the look anyways but is already fixed. Thanks anyways.
It was a line of code in a script sourced to by KDE Plasma's .xinitrc that did set QT's theme style to GTK2, effectively wreaking havoc in Plasma.