By accumulating resources for the future, we give increased power to whatever decision-makers in the future we bequeath these resources. (Whether these decision-makers are us in 20 years, or our descendants in 200 years.)
In a clueless world, why do we think that increasing their power is good? What if those future decision makers make a bad decision, and the increased resources we’ve given them mean the impact is worse?
In other words, if we are clueless today, why will we be less clueless in the future? One might hope cluelessness decreases monotonically over time, as we learn more, but so does the probability of a large mistake.
Indefinite accumulation of resources probably also increases the chance of being targeted by resource-seeking groups with military & political power.