Earlier quoted context omitted.
I can second the issue with the automatic color selection; with my background photo it cashes out to an illegible black on black, and there's no (obvious) option to change the theme or override the computed colors. It seems like it would be relatively straightforward to honor the user's light mode/dark mode setting, and the WCAG accessibility guidelines [1] do a good job of both discussing the importance of luminance…
Hey. I'm seeing this issue with some other users as well and I'm trying to reproduce this - do you have the reduce transparency accessibility option enabled by any chance?
edit: Checking now I'm back in arm's reach of my laptop, I can further confirm disabling the option does resolve the issue on Sonoma. Nice catch!