WP_Query on custom field and order results

Change your code with this and might help you with what you are looking for. The issue here is that we cannot include key, order and orderby in meta_query. But if you want to order you result posts based on key than you can pass the query arguments as below:

$custom_query_args = array(
    'post_type'         => 'mcg_event',
    'posts_per_page'    => -1,
    'order'             => 'ASC',
    'meta_key'          => 'event_start_date',
    'orderby'           => 'meta_value_num',
    'meta_query'        => array(
        array(
            'key'   => 'event_status',
            'value' => 'archived',
        ),
    )
);