I understand that.
This isn't "newest is best because it is new". It is the simple fact that Gygax, et al, were quite visionary, but... they were newbs. We have learned a whole lot about RPGs since their work, and their original game contains none of the learning of the following years. That's not a failing on their part, any more than it is was Henry Ford's fault that he couldn't produce a 21st century automobile, or Newton's that he didn't figure out Relativity.
Nor does this mean their games aren't fun - I got years of enjoyment out of them. But... we do better now.
I disagree. You are comparing art to technology. Sure, there may be improvements in some ways but that does not make art lesser than it was.
Because we now have Olafur Eliasson or Mark Kostabi does that suddenly make the works of Michaelangelo or Rembrandt suddenly devoid of being appreciated or valuable pieces of art? Does it mean that suddenly because art has advanced in it's form that people must prefer Eliasson or Kostabi to the other two. Is Da Vinci's Mona Lisa now dated to be worthless in usage compared to the other because it's outdated by several centuries.
This is something you see in game and game design regularly at times where someone claims old games are outdated and new games and hotness are better.
Looking at games themselves, as per I read the ideas in how they were presented regarding model T's and current cars, Chess and Go are fallen games that are no better than century old pieces of technology, no longer able to keep up or be as good as those games made today. Contrasted to that, many would disagree and would say Chess and Go are perhaps the most popular games on the planet today outstripping the "new" and "improved" versions of most games with the updated "game designs" of today.
However, I don't think the 5e designers felt the same way you did. They WANTED to capture the ideas and design ideas of the old and present them in such a way to modern audiences.
It's more of an art and preference than technology in my opinion which is why at times, the same ideas remain popular today as they did previously.
This is one of the things that 5e tried to build upon, to find and retain that which made D&D popular in the past while adding on things to attract modern audiences.