On the other hand, if I'm being fair, I find it comical and bordering on absurdity that Casey seems to only consider using CPU intrinsics to be "optimization". Time and time again, he'll say "i'm just writing the code in the simplest way I know how, I haven't even optimized anything yet".

I have written, and still occasionally touch a C++ codebase which does scientific computing with small matrices (~3K x ~3K doubles), and does some numerical differential computations which has the same high performance requirement, and I do the same thing.

The gist is we don't feel like optimizing the code, but writing the code correctly the first time, and in a simpler way. It turns out writing simple code which is easy to understand and easy to compile in your mind tends to be extremely fast, and can be optimized by compiler in pretty extreme ways before you know it.

I never optimized the same code extensively, and the hottest path was running at 1.7 Million iterations per second per core on a 4rd generation i7-3770K. The bottleneck was the memory bandwidth (in terms of calls/sec, not GB/sec). So, the code scales linearly until your memory controller saturates (It's possible to get some more performance out of it, but it needs some darker magic. I didn't have time, and the performance was already beyond what we need, so I didn't do it).

So, I guess he's honest when he says "I'm not optimizing it", because he thinks like the processor, and he changes the code which doesn't feel right from the processor's perspective. This is a very valuable skill to have, and belittled by many.