I dont know much about web design but the site is probably burdened by being very old. The layout is executed using a combination of classes and CSS but most of what an article needs is baked into the HTML spec these days. For example <aside> tags and stuff. There are custom CSSs for the website on GitHub and they turn out to be more complicated than expected because of how the pages are designed.</aside>
It's not. Works by various authors have different html formatting that make it very difficult to consistently scrape. Splitting works into several pages makes it impossible to send them to pocket (or FOSS equivalents). It sucks for anything other than reading in their website.