Igor Benic offers some great tips for getting better as a WordPress developer. Excellent points about code reviews and just reading the available handbooks. Taking time to learn from others and building extensions for existing plugins are good ideas too. 💯
If you want to learn how a plugin has fared over time, take a look at Igor's project, getactiveinstalls.com. It tells you the number of active installs for any WordPress plugin in the repo as of a date you specify.