For some users, using a mouse or a trackpad presents barriers. Therefore, an important element of making a website accessible is to be sure that every link or interactive element of the page is accessible using the keyboard alone. This includes the primary navigation (including dropdown menus), all of your links and buttons or anything that other users might click on to get a result or navigate to another page.
It’s simple to check your page to ensure it is accessible by keyboard alone. Simple tab through each element of the page. As you tab through, you should be able to track where you are visibly. If you do not see a visible square around the links or navigation elements, this indicates there is a problem with the code.
Keyboard accessibility satisfies success criterion 2.1.1 of WCAG 2.1. Visible focus satisfies success criterion 2.4.7.
Absence of either of these would be considered a failure to meet very basic elements of web accessibility.