It's simply not realistic to expect the entire world rewrite its entire technology stack from scratch, starting at the transistor level on up every time there's a new industry innovation in security or performance.

LLMs might make this somewhat easier, but you're still going to have to deal with backwards compatibility and legacy systems. Completely eliminating the use of architectural cornerstones like x86 or HTTP or even PHP across the entire industry isn't going to happen anytime soon, let alone overnight, especially if the only argument for doing so is "we could design this better if we implemented it from scratch".