It's time to say something!
i use last fm every day and i'm scrobbling a lot of music.
so this extension i use for years now (changing red to middle blue), togehter with the user css syle from Gomgon on github (Stylus extension needed) makes a perfect readable and dark last fm site.
Thanks for sharing it with us!
Maybe you make an advanced version in the future combining dark style from Gomgon with your one?

Last.fm user since 2004, thanks for this addon, wish I'd found it earlier! Rolls back some of the horrible UI choices in the great redesign of 5 or 6 years ago...