In the message list view, change the colour of the date/time to be a different colour; perhaps blue (similar to Outlook or Edison) or customisable.
This will make seeing unread emails at a glance easier.
The current option to have a different colour background for a message in the list, especially in dark mode, looks clunky, dated, and (in my experience, most importantly) messes with my ability to smoothly read the list of mixed read/unread messages.