Microsoft Teams updated across our workplace this week (over 10,000 users) and introduced these obnoxious white bars. Making the "Dark" theme comparable to the "High Contrast" theme unnecessarily. The "Light" theme does not show harsh black lines to divide the sidebar, it just shows a slightly offset light-grey to make the distinction.
Likewise, the Windows "Settings" view and other default apps use a dark grey for the sidebar menu (#1f1f1f) to offset the main content section (#000000), no high contrast divider. Teams should remain modeled off of these.
I would personally prefer to see customizable XML/JSON templates so we can customize the color values for each component. It makes little sense why that isn't an option in this program in the year 2024, either as a UI "customize the color scheme" or just backend template file.