Bruh, KDE Plasma 5 had its initial release in July of 2014, and because it's open-source, the first screenshots were public even before then: https://kde.org/announcements/plasma/5/5.0/
Windows 10 got initially announced two months later, and still looked a lot like Windows 7 back then: https://blogs.windows.com/windows-insider/2014/09/30/announcing-windows-10/