Add fluent design elements.
Microsoft Teams is partially UWP App so i suggest to add some fluent design elements for better look.
Seyyed Soroosh Hosseinalipour commented
I think, better approach is to complete rewrite in UWP framework.
Mark Szili commented
Yes fluent is needed with some acrylic blur and ability to sync to the overall Win 10 window theme settings. A proper dark mode with black background, NOT grey, and no I'm not talking about high contrast.