I remember in XP, Vista and 7 using the UXtheme dll mod to get third party themes. First the loss of the sidebar then the drop-off of themers. I skipped 8 and by 10 I'd had enough. Didn't really come back to theming until I made the jump to full-time Linux in 2022. Theming support being there by default in KDE is amazing. I miss the 2007-2018 themes but Oxygen keeps me happy for now.