Developing a beautiful WordPress theme is not easy or everyone would be doing it. You need to know your WordPress, PHP, CSS, JavaScript, and other technologies to succeed. Many of us use themes available online without paying attention to their codes. Tools such a Theme Mentor can help you with code analysis. It looks for problem areas in your code and suggests how you can fix them.
I don’t believe we were able to find too many themes that were not flagged by Theme Mentor. The script goes through your code and tells you when you don’t have calls to wp_header or wp_footer. It also makes some suggestions on how you should handle your script tags in other parts of your site. What’s neat is you can analyze multiple themes using the appropriate drop-down box fast.
Just because this plugin finds a ton of issues with your theme does not mean your template is hopeless. Theme developers do need to take time to get themselves familiar with best coding practices to avoid problems down the road though.