While we understand your anger, Default Template was removed and replaced with Default Revamped designed by Xemah which provides a much better design concept. Pretty much all the available templates available have some sort of dark mode support. If you would still like to use the old Default Template you can use this. I am sure you could see if module creators could still support the template but I don't know how lucky you will be as it was kinda "phased out" from this point forward.
the problem is this:
The revamp design offers NO setting with which you can set the dark mode directly. You definitely need CSS knowledge to edit the colors, i.e. for a CSS layman it is not particularly easy to change something.
The good thing about the default theme was that different designs could be selected there. And Bootstrap4 is no longer supported by the module creators due to the removal of the default theme.
Great system! Having basic web design knowledge its easy to open up the files and change things here or there where I need it to. Thank you for your work! and Happy Holidays, cant wait to see the updates. I'm waiting for ColdFire to finish with updating Aether to pre8.