This entire website is fantastic. There is so much detail to be had and the articles are very readable.
I would actually argue the inverse. There are many articles that are still very relevant, some just don’t realize it since modern engines abstract the logic away. But there are some developers that work in engines that still need that knowledge. BSPs, VFSes, raytracing, 2d blitting techniques, 3D mathematics, etc are all still very useful.
This is one of the reasons I’m so glad these archives have stayed online for so long.