
My workaround has been to set my laptop's brightness to 100% whenever I need to find the active tab & background is like this. But that's no way to live a decent life :-(
I don't know what Apple's pre-occupation with translucency is when it comes to the Safari address bar, Favorites, and tabs. I have seen their 'explanation' of wanting to provide more space for content - but in this case, it's just the appearance of more space for content - at the real expense of usability.
I already had to give up my usual Dark Mode setting when I started using Tahoe - because in dark mode, the problem is even worse. It's a bit disconcerting how little usability testing seems to be going on at Apple these days.