Defer all CSS in WordPress (with exclusions)

defer_all_css.php

function sz_defer_all_css_but( $tag, $handle ) {
	if (is_admin()) { return $tag; }
	$handlestoexclude = [];
    if ( !in_array($handle, $handlestoexclude ) ){  
		$dom = new \DOMDocument();
        $dom->loadHTML($tag);
        $csstag = $dom->getElementById($handle . '-css');
        $csstag->setAttribute('media', 'print');
        $csstag->setAttribute('onload', "this.media='all'");
        $csstag->removeAttribute('type');
        $tag = $dom->saveHTML($csstag);
  	}
    return $tag;
}
add_filter( 'style_loader_tag', 'sz_defer_all_css_but', 10, 2 );