"I am not a prophet in any sense of the word, and I entertain an active and intense dislike of the foregoing mixture of optimism, fatalism, and conservatism"

Herbert Croly is expressing his disdain for the combination of optimism, fatalism, and conservatism. He is making it clear that he does rule out himself to be a prophet, which he does not agree with the idea that these 3 ideologies ought to be blended together. He thinks that optimism and fatalism are 2 opposing forces, and that conservatism is a third, separate entity. He is suggesting that these three ideologies ought to not be integrated, as it could result in a hazardous and potentially destructive outcome. He is likewise revealing his intense dislike for this mix, which indicates that he thinks it is a bad idea. Ultimately, Croly is warning against the risks of mixing these three ideologies, and is promoting for a more well balanced method.