It’s just that in Silicon Valley, you can’t merely make a better typewriter and sell that at a profit. No, you have to DISRUPT. You have to REINVENT. Well, at least you need the appearance of that, while you squeeze eyeballs until they pop out enough advertising dollars to give the VCs that 10x return.
The codebase on big sites isn’t impenetrable because developers slavishly followed arbitrary best practices. The codebase is broken because developers don’t talk to each other and don’t make style guides or pattern libraries. And they don’t do those things because the people who hire them force them to work faster instead of better. It starts at the top.