I agree that the original gives the dated impression to the website, but I believe that is entirely because there is a background texture present. Repeated background textures immediately make any website appear very dated unless the website is going for a modern brutalist look (which I very much do not recommend).
To test that hypothesis, I simply replaced the background image with solid colors and I think it immediately gives it a cleaner and more modern look than all 3 options above. The lines separating the items could be colored with the red or given a lighter gray, but their presence gives the theme a much nicer and more accessible separation between threads. I agree with @Neopopulas that it's not distinct enough between entries without the lines.
Option #3 sadly looks more dated than #1 to me. I've been sitting here trying to figure out what about it doesn't sit well with me in a way that is constructive and not just, "I don't like it." I really like the solid color background and I think the color choice of that gray is a really good background color for a different theme. The header color doesn't feel right, though.
With that said, I think these are the primary issues I have with #3
- The centered header does not feel quite right for the design
- The narrow spacer between the header and body feels a bit out of place
- It's weird to me to visually see more space between the bullets and the thread information than there is between the threads themselves
- The colors don't go together very well, but I think that could be due to the gradient used on the headers
I think #3 has promise if tweaked a bit more.
Option #2 seems like the worst of both, personally.
I hope that was taken as helpful and constructive rather than just complaining.