You have a great browser, Mozilla. But, you err in making changes we do not want. If someone wants a black background in tabs, let them use an addon. It is hideous. And, I don't want to have to keep up with upgrading another addon. So, I have to look at this hideous black on my computer every day all day long. And, I have to find other icons now that you have moved them. And, to add a tab, I have to move my screen so I can find the + since you now have chosen to make it white and almost invisible.
Listen to your users and correct the mistakes soon. And, we don't want you to violate our privacy as has Microsoft and Google.