It's not horrible.
The purple for the icons should be lighter, you cannot really read them. Also, why is it purple? Nothing of your theme has purple in it other than the icons - it just doesn't match your color palette. Make the colors match. Right now you have a header with like 5 different shades of blue, which do not even match the title bars; let alone the purple. Dark themes are hard to make without making it look tacky. You've done well with it being tacky.
Remove the purple, find dedicated color palettes, and start changing colors! Also, the background is a lig