Shared hosting puts your website on a server with hundreds of other sites. When one of them gets a traffic spike or runs a poorly coded plugin, your site slows down. There is no isolation, no guaranteed resources, and no way to fix performance issues yourself because you lack root access.
A VPS changes the equation entirely. You get dedicated CPU cores, RAM, and I/O that are yours alone. Install Nginx instead of Apache. Use PHP 8.3 instead of the ancient version your shared host offers. Configure Redis, Memcached, or Varnish for caching. Every optimization is available to you.
AnubizHost VPS also removes arbitrary limits. Shared hosts cap your inodes, databases, email accounts, and addon domains. On a VPS, you host as many sites, databases, and email accounts as your server's resources can handle - with no artificial restrictions.