Removes the !important

important_filter.php

<?php
/**
 * Lowering specificity of WordPress global styles.
 */
add_action( 'init', function() {

	// WP5.9+ only.
	if ( ! function_exists( 'wp_get_global_stylesheet' ) ) {
		return;
	}

	// Dequeue original WP global styles.
	remove_action( 'wp_enqueue_scripts', 'wp_enqueue_global_styles' );

	// Enqueue WP global styles early.
	add_action( 'wp_enqueue_scripts', function() {

		// Lower CSS code specificity.
		$stylesheet = str_replace( [ 'body', '!important' ], [ ':root', '' ], wp_get_global_stylesheet() );

		if ( empty( $stylesheet ) ) {
			return;
		}

		wp_register_style( 'wp-global-styles', false );
		wp_add_inline_style( 'wp-global-styles', $stylesheet );
		wp_enqueue_style( 'wp-global-styles' );
	}, 0 );

	// Treat also editor styles.
	add_filter( 'block_editor_settings_all', function( $editor_settings ) {

		// Lower CSS code specificity.
		$editor_settings['styles'] = array_map( function( $style ) {
			if ( ! empty( $style['css'] ) ) {
				$style['css'] = str_replace( [ 'body', '!important' ], [ ':root', '' ], $style['css'] );
			}
			return $style;
		}, $editor_settings['styles'] );

		return $editor_settings;
	} );
} );