aim of a decision theory [...] to maximize an objective function
Pragmatically, this is also the wrong thing to do if pursued too methodically, because a legible objective function is always only a proxy for what is actually valuable, and optimizing for a proxy ruins it. A better ethos might be to always remain on the lookout for improving the proxies, while only making careful use of currently available ones, perhaps in a way that pays attention to how unusual a given situation is.
Pragmatically, this is also the wrong thing to do if pursued too methodically, because a legible objective function is always only a proxy for what is actually valuable, and optimizing for a proxy ruins it. A better ethos might be to always remain on the lookout for improving the proxies, while only making careful use of currently available ones, perhaps in a way that pays attention to how unusual a given situation is.