Active and inactive window frames look the same

Firefox and Gnome Terminal window frames look the same whether they are active or not:

Why is this? How can I change this?

Debian 12 bookworm, Gnome Shell 43.9, default light theme.
gnome-terminal 3.46.8-1

That does not look like the Adwaita gtk3 theme. Are you sure you are not using some custom theme?

You are right. In gnome-tweaks I found “Old applications” was set to “TraditionalOk”. Setting it to “Adawaita” makes them look the same.

Must be a leftover of me copying my home folder from the previous computer.

Thank you.