We constantly tweak WooCommerce to make it more performant. Performance issues can however also be server related.
WooCommerce is a big plugin and although we develop it with performance in mind it will put a slight increase on your servers memory usage.
It also depends a lot on what your server setup is, if you have a pretty stock standard hosting plan, then you can expect it to lower page load time as your site will require a bit more memory meaning it can cause slower response times.
Things like having an object cache like Redis or Memcache in place and running master-slave database setups will definitely speed things up.
If you can pinpoint what is causing this then please do inform us and we will gladly investigate this further.
