Hi Loke! Thanks for stopping by.
jQuery (slim) is primarily there because of legacy reasons. When we launched Hashnode (2015), we used a few jQuery plugins and took help of jQuery's xhr to make API calls. After that when started using React heavily, we tried to minimize the usage of jQuery and at one point we made it a point not to use jQuery for new features and started rewriting old bits of code that were using jQuery. For example, all the XHR calls were replaced with fetch with a polyfil. Some widgets were rewritten using vanilla JS. Today we don't use jQuery for new features. However, we still have a few areas that are dependant on jQuery and we'll need some more time to fully rewrite them. :)
We have cached all our static assets in Service Workers. So, for a logged-in user there won't be any network delay because of jQuery bundle (after the first visit of course). But yes, we'll get rid of it soon. 🙌