One area that could use improvement is the votes section for plugins. With so many plugins that claim to do the same thing, it can be hard to find the right one. The votes currently don't lend much to the decision as they're always so low.
As I look through plugins I can't live without the number of votes is always startlingly low. Even popular plugins like Jetpack and Akismet have just over 1000 votes - but have surely been used over 100,000 times!
A couple ideas I have to increase votes:
1. Integrate the number of plugins voted on into the WordPress.org profile more prominently
2. Have a progress bar in the WordPress admin bar for Admin level users to show them what percentage of the plugins they've rated.
3. Make it easy for plugin developers to include the star rating system into their plugin, or maybe on the actual Plugin listing page inside WordPress
WordPress has one the largest and community of any website platform, making it easier for users to rate plugins (and heck, themes) will only make the platform and its add-ons stronger!