I like it and would not call it outdated. Only thing I recongnized is that it's way too dark.
Maybe you could do a background more light...
Best regards
I've been thinking about doing it in more colors, but don't know what would look best.
The one I have now is:
Windows/buttons: #343D91
Light background: #888888
Dark background: #777777
Light/dark gradient: #AAAAAA/#808080
Dark/light gradient: #808080/#AAAAAA
Text: #FFFFFF
Dark part of outset borders: #424242
Light part of outset borders: #BBBBBB
My advice: Turn the black border arround forum into grey or blue.
Do grey background for text area/boxes or selections (E.g. Quick language)
It's hard to say exactly what makes it look so dated. It's not that tangible. The background image is definitely standing out to me as the biggest factor, but ultimately it's just a culmination of the colours and design choices.