Custom endpoint in REST API - Wordpress

I have a WordPress website and I want to add a custom endpoint that sends the metadata of the users.

Important: The already API works only by calling it like this "domain-name.com/?rest_route=/wp/v2/users/". I know that for the API to work properly the standard solution for a custom endpoint is to change the permalink settings from plain to post.

Is there any solution without changing that setting?

The standard pre-built endpoints work fine when I call them like in the above example.

For example this code only works for the wordpress websites with the permalink settings as post. Calling the api like this (domain.com/wp-json/wp/v2/custom-ep. If I place the same code in the other website with permalink setting and call it as mentioned above ("domain-name.com/?rest_route=/wp/v2/users/"), I will get error 404.

code:

function create_custom_endpoint()
{
    register_rest_route(
        'wp/v2', // Namespace
        '/custom-ep', // Route
        array(
            'methods' => 'GET', // HTTP method
            'callback' => 'get_response', // Callback function
        )
    );
}

function get_response()
{
    // This is your custom response data
    return 'This is your data!';
}

// Hook the custom endpoint registration to rest_api_init
add_action('rest_api_init', 'create_custom_endpoint');