This quote from Why mobile web apps are slow is not at all deep or mysterious, but its understatedness brings about lighthearted remembrance of past foibles with dynamic languages:
If your C program executes in 10ms, then a 50ms JavaScript program would be “near-C” speed. If your C program executes in 10 seconds, a 50-second JavaScript program, for most ordinary people would probably not be near-C speed.