Are there any WordPress websites that have scored over 90 on Google's PageSpeed Insights?

Yes, this is possible, and there are some ways to do this.
-You have to dequeue unnecessary js and CSS files loading on the landing page.
-Use premium page cache plugins, and follow their instructions.

Dequeue CSS, JS
-In your functions.php file use the hooks to dequeue files

 /*Site optimizations*/
/*Site optimizations*/
function remove_unnecessary_assets() {
    if (is_front_page()) { // only remove on the home page

        // remove CSS
        wp_dequeue_style('style-handler');

        // remove JS
        wp_dequeue_script('script-handler');
        
    }
};
add_action( 'wp_enqueue_scripts', 'remove_unnecessary_assets', 999 );

After removing CSS, JSS make sure your site is working fine.

Then, use cache plugins:
Wp Rocket OR
Nitropack

Check Wp Rocket site on Google’s PageSpeed