Curation rewards are fine. Downvotes are part of the mechanism, including for curation rewards. If you expend your valuable vote power pushing rewards up excessively and/or indiscriminately and downvotes then follow, your curation rewards are reduced. Higher profit comes from upvoting where there is consensus on the resulting reward, which may indeed require more effort to find content where the rewards aren't already high, as opposed to picking something more or less (or entirely) at random from "Trending" and pushing it even higher.