// Clean the up the image from wp_get_attachment_image()
add_filter( 'wp_get_attachment_image_attributes', function( $attr )
{
    if( isset( $attr['sizes'] ) )
        unset( $attr['sizes'] );

    if( isset( $attr['srcset'] ) )
        unset( $attr['srcset'] );

    return $attr;

 }, PHP_INT_MAX );

// Override the calculated image sizes
add_filter( 'wp_calculate_image_sizes', '__return_empty_array',  PHP_INT_MAX );

// Override the calculated image sources
add_filter( 'wp_calculate_image_srcset', '__return_empty_array', PHP_INT_MAX );

// Remove the reponsive stuff from the content
remove_filter( 'the_content', 'wp_make_content_images_responsive' );