This is a good website. It's not terribly heavy, it doesn't have a lot of slow rendering, and it has clear UX. Any recommendations below are for performance and UI enhancement, and are at most high priority rather than critical. Still, there are improvements to make that will yield much better performance and usability for not much effort.
The site is very competently built and served in most ways. The origin server (Apache on Ubuntu) is reasonably fast. Response times are acceptable. And the site behaves well on mobile devices.