I'll try and list some of the things that pop out to me. I'm not a designer either, but I'd like to think I can spot some nice designs when I see them.
The old site didn't put things into boxes. next.sabayon.org has everything in a box. The horizontal dividers make sense, but why do we need vertical dividers on the left and right side, to box that content in. That seems like a very old style of website.
doesn't do that, at least not on their homepage. Even on pages like https://wiki.archlinux.org/
where a lot of the content is boxed in, there is still content on the non-boxed in part.
doesn't do it. https://www.ubuntu.com/
doesn't do it.
They just use whitespace to clearly separate different sections of the homepage. But boxing everything in is prevalent in every page on next.sabayon.org That's only thing that really irritates me. Again, maybe it's a personal taste thing, but I see more and more sites moving towards using whitespace and natural changes instead of hard lines and boxed in text to separate different content. And that's what the current site does better.