Making a WordPress site without using any plugin is near to impossible and unimaginable, because WordPress plugins are great ready-made code libraries which can built features for you with just single click. WordPress plugins are exists for extra functionality.
Ways to remove plugin js or css
1. De-register – Remove plugin js or CSS
Remove plugin js or css using wp_deregister_script() and wp_deregister_style() methods. The option will work most of times.
2. Remove plugin js or css by removing action
If deregister methods not working for you then you can try by removing action. Some plugin are not built with recommended way as styles and js are not included with wp_enqueue methods. Then you can use remove_action() method.
It is very tedious task when you have additional styles or scripts loaded from any plugin and that messing up the content on your site. Sometimes even deregistering them is not enough as well. If methods shown above to remove plugin js or css then feel free to ask for help using comments and I will try best to help you in resolving issues.