I was bored (procrastinating from exam preparations...), so I went ahead and created a simple light userstyle that people who really want it can use, until the official one comes out in 10 years
It totally doesn't cover the entire forums yet, but the "main" parts (browsing categories, reading threads, viewing people's profiles) should look fine.
How to use it:
1. Install Stylish, or whatever user style manager you prefer.
Here's the link for Stylish for Chrome.
2. Install my light GameMaker Forum userstyle.
Here's the link to it.
EDIT: I improved it a bit. Please uninstall and install the userstyle again.
Preview: