&gt; <i>programming languages are relatively fungible</i><p>I agree with that regarding learning them, but I disagree strongly when it comes to the end result.<p>I make a lot of my money fixing&#x2F;replacing PHP projects. As has been pointed out many times before, there are issues with PHP that are guaranteed to cause bugs. The same is true of many languages.<p>But there is a spectrum! Some compilers&#x2F;interpreters scream at you and terminate if you contradict yourself. Some of them even recognize security vulnerabilities.<p>I agree that people skills, domain knowledge, and architecture are hugely important, but great teams are still less effective when they use slow or confusing tools.<p>You might be the greatest contractor in the world, but if someone asks you to build a skyscraper with plywood and super glue, you&#x27;re going to end up with something dangerous, fragile, and guaranteed to fall apart as soon as someone tries to use it.