The Torah does mention reward and punishment.
Many times the reward and punishment is for the nation as a whole like in the second paragraph of the Shema or it also is meant as in the next world as in the reward for shiluach haken or cibud av.
I see the mistake as a misunderstanding of the tremendous peace and calm that deep emunah and bitachon can bring to people who would not be expected to be peaceful or calm! Is it really a reward if only good things happen to a person and he is happy as a result? I don’t think this can compare to happiness of a maamin even in the midst of many struggles. Sheva yipol tzadik v’kum.