My problem with Casey is that he is not a performance engineer, he is a performance maximalist. Software is a set of tradeoffs. If he truly cared about performance, the best thing for him to do would be to write clean code that had good performance, but he refuses to do that, since it's hard. Instead he insists that the only way to do performance is to write unmaintainable code which ironically enough makes it difficult to do performance optimizations because it's hard to lean on abstractions that allow for things to be refactored.