[Desktop app] Worsen UX with new themes from March 25

The changes were made are reducing visual clarity and overall make user experience worse.
1. Reduced contrast between the titlebar and other panels makes harder to distinguish the application border from other applications, now it's easy to loose discord window. 
2. With reduced icons' size, it's harder to hit them, and saved horizontal space is not needed, especially in exchange of such inconvenient change.
3. Bottom left widget (personal card with mute and settings buttons) is overlapping servers that makes server navigation harder.

Part of changes could be a theme and sizing settings, so It would be nice to have it back someway.