Images overall are way too large.  I bounce around to different desktops from 29" to 15" monitors, from desktops to laptops to tablets, and in ALL of them the images are just too humongous to be navigatable.

Preview images of items are extremely large, and even on at 1900x1080 resolution you have to scroll up and down to see the entire image.  What ever happened to lightboxing the images so they self-size based upon your system settings?

It is like somebody's first attempt at web design and did not know any of the tricks about self-sizing images, setting multiple display options to show more than 2-3 images per row in the Marketplace, and even sizing down the fonts and using "web-safe" colors.  Back in the day sites were designed around 640 pixels, then 800 became the standard.  Nowadays you can make a website designed around 1024 or 1280 and be fairly safe, but it looks like whomever designed this site had at least double that resolution or was working off dual monitors.  "Know your audience" should be the first rule of the design...and in this case the site if failing.

If the intent is to drive away vendors and shoppers because they cannot find anything easily, congratulations, you have succeeded, but if you really intend for the site to be functional, realize some changes are not good, and there were good points to the old design.  I'm not saying it was perfect, but it was at least functional compared to the current design.

 

Overall, three main things can make the site much more user-friendly:

1. Automatic sizing of preview images to suit different monitor resolutions

2. Ability to decide how many images per row you want to see

3. Go back to the old "breadcrumb"/filter/search engine

 

These three simple changes would eliminate the vast majority of complaints with the users. 

And don't get me started on the forum font and space sizes!