WordPress is the most popular CMS in the world and consist of a lot of scripts and plugins. It should work fast to be in good positions in the search engines.
Furthermore, Google announced at July 9, 2018 that using page speed in mobile search ranking is now rolling out for all users.
Scripts run optimization
WordPress uses PHP for scripting. So the three main steps should be done:
Enable PHP code cache
PHP caching could increase response time by about 50%. There are detailed steps how to check and configure PHP script caching.