class Action is deprecated

I am following a tutorial about Magento version 2.4.2 , and I am getting a problem while using Action as It shows deprecation ,
and also even after cleaning cache , the error shown is Required parameter ‘theme_dir’ was not passed

This is my code if anyone has an idea

<?php
namespace SimplifiedMagentoRequestFlowControllerPage;

use MagentoFrameworkAppActionAction;
use MagentoFrameworkAppResponseInterface;

class CustomNoRoute extends Action
{

    public function execute()
    {
        echo "this is our custom 404";
    }
}

Thanks in advance