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.
I remember when compact was hidden - apparently this was a change driven by telemetry. It was possible that there’s an overlap between those who use compact and those who turned off telemetry. I wouldn’t be surprised if something similar also occurs with Pocket being left on too.
If compact breaks in a future update, it’ll probably be removed altogether. At that point, best option would be userchrome customisation.
IIRC, this change was made ahead of the impending UI overhaul. This combined with the Windows 11 getting bigger touch-friendly UI elements understandably didn’t sit well with many people.