Nice rant, and I mostly agree with it, but there are a few slow things about the ways that some languages are usually implemented that don't really have much to do with over-engineering. Let's take this line of Python code, for example, and look at how the CPython interpreter runs it:
return x + 42
This turns into the following bytecode instructions:
LOAD_FAST 0 (x)
LOAD_CONST 1 (42)
BINARY_ADD
RETURN_VALUE
First we get the x variable from the local namespace. This is an array of PyObject pointers; the LOAD_FAST oepration simply does an array lookup and puts the result on the stack, incrementing the reference count. Pretty fast. Next is LOAD_CONST, which is even faster; it takes an already-allocated PyObject and puts a pointer to it on the stack, incrementing the reference count. BINARY_ADD removes two numbers from the stack, dereferences the pointers to get the integer values, allocates a new PyObject with the resulting integer inside, bumps up its reference count, decrements the reference count of the two operands, and pushes the result on the stack. Finally, RETURN_VALUE jumps back to the caller of the function.
In Go, the corresponding code would be compiled to two, maybe three machine code instructions. There are good reasons why Python does it this way, but it does suffer some inherent slowdown.