Using the dark theme on current Nightly versions (version 90, Linux) it's really hard to see which tab is currently active. Notably, all other default themes (system, light, Alpenglow) have well-distinguishable style for active tabs, this issue is specific to the dark theme.

A picture taken via my phone from the normal view position in front of my screen is showing the issue even more drastically...

(Note that in both pictures, I'm fine with the contents "leaking" into the public, even if they show my view of Matrix and an open history menu that I used to show in the Matrix channel how I find the spacing on the items to be somewhat too large for my feelings - which if anything is a different bug)