Update from the 26th of November 2021
For the context, the HTML5 specification has been officially completed in September 2014, even though drafts and recommendations were online for the previous 7 years. Good tech does not guarantee a visually pleasing website: indeed, HTML5 is supposed to help with semantics and structure, not style and interaction.
Also be kind and do not judge books by their cover. While the design does not follow the latest and greatest innovations, the contents are educational and have certainly helped a fair share of students.