You can change the url prefix to something else, see: https://docs.mendix.com/refguide/app-settings/#url-prefix, however, it can not be empty:
The URL prefix must be alphanumeric and can not be empty, whitespace, or be any of the following values: 'ws', 'ws-doc', 'rest-doc', 'odata', 'odata-doc', 'api-doc', 'xas', 'reload', 'file', 'resources', 'img', 'fonts', 'css', 'js', 'pages', 'preview', 'nanoflows', 'layouts', 'widgets' or 'dist'.
That is simply how the page URL in Mendix works. You can read about it in the documentation here:
I don't believe there is currently a way to use the built-in page URL without using the /p/ in Mendix 9
The areas where the configuration has not been modified are in the App Setting