Don't worry there will always be geeks who learn HTML and CSS just for the hell of it.
To be fair, despite the myths, there are probably no ancient skills that can't be performed better by modern-day craftsmen and women.
That is with modern tools and technology. Try building the pyramids or Petra with what they had today. But also, the situation can not be compared.
Take these trades/professions = Farming - people experimenting with seeds over time became skilled farmer profession with simple tools and natural solutions utilizing what they have immediately in their vicinity, became farmers using machines and fertilizers, and in the future it may be all automated machines.
= Metal working / tools - simple tools with sticks and stones to make tools, combined eventually with mining, surveying, and forging, (all different professions), then you have blacksmith, then industrial revolution has machines doing most of the hard work but still humans operating the machines and involved in every step of the process, in the future humans may be eliminated from quite a few of the steps with automation and robotics.
= computer programming = binary, cobol, C, if you look at the history and evolution, modern programming methods and languages came from the early ones. The best way I can think to explain the future problem is this.......this website itself. It could have been developed using templates and help. A button that indicated to insert a text box, how to store the information into the database, etc. But behind all of that, HTML, asp, java, SQL, etc were used even though the person who built it would not have needed to known them. If suddenly had to start from scratch, if they did the same work they did, had some template with commands, it would all do nothing without all the backend coding that was automatically written. In the far future from now, how many templates upon templates, and languages upon languages will be written and made, that allow people to make electronics and programs that using todays technology would have taken thousands upon thousands of hours. Or imagine building a website coding in binary. If all computer technology was wiped out today, people still alive who were part of the original buildup of computers. They really started to advance in the 60's + then in the 80's for personal computers, etc. Books, people, etc, all still alive and it could be redone. But when technology advances quickly, and hundreds+ years from now, binary, cobol, c, still in the very deep roots but they are long forgotten. While all of that is happening, robotics are taking over all trades and much of human labor that even today at least has humans controlling the machines. If something happens to wipe out that technology, then unless it was somehow well preserved, not in electronic form only, or not in decayed books, many things can be back at square one.