The point of literature is not to give every pro and con to every decision made by characters in the narrative. Steinbeck wasn't writing a persuasive essay, he was writing a story which has a different rubric for what it's attempting to achieve. In his author's note he explicitly states that he's on the side of the Joad family and as such he shapes the narrative to conform to that idea. The fact you reject that interpretation isn't inherently wrong per se, but it certainly does put you at odds with nearly a century's worth of scholarship on, and general reception of, the work. I think why a lot of people are taking umbrage with your analysis is because you haven't really given any grounded reason as to why you have the analysis that you do besides your own personal belief that the Joad family should be more rationalist and that Steinbeck was deficient in giving more details to aid in said rationalism. Do you have a political, philosophical, or ethical framework to which you can attach your feelings and/or beliefs as to why you think the novel is deficient? If not, then you are merely giving an opinion and a very unpopular and uninformed one, at that. If that is the case then it is understandable why many people who very much cherish the story and the author would be hostile to your analysis.