The IPCC et al was intentionally conservative in its predictions because even the conservative estimates suggested it made economic sense to fix the problem.
Like getting shot is bad. If a scientific and economic consensus tells you to put on a Kevlar vest, you do it.
They shouldn't really need to detail all the other things that could go wrong if you get shot, because the conversation should already be over and you should have the vest on, which means even if you do get shot things will probably go better for you and you now have the mental energy to work towards not getting shot.
I think you are mis-reading your parent comment. They are saying we should be humble when it comes to predicting all the things that could happen when manipulating such a complex system as the climate. If our best science is saying there are at least 6 different ways in which we are already causing harm, then it stands to reason there are probably more dangers than that that our science can't yet predict. I think they are saying, let's always assume there are details that we won't understand and act on that basis, i.e. put on the kevlar vest and work towards removing carbon gases from the atmosphere.
I was agreeing with them, just with some more details of why we (sensibly) haven't spent even more effort on cataloging all the terrible impacts of climate change in extreme detail. What we know is bad and convincingly supported enough and bad political actors will seize on anything they can portray as an overreaction.
Like getting shot is bad. If a scientific and economic consensus tells you to put on a Kevlar vest, you do it.
They shouldn't really need to detail all the other things that could go wrong if you get shot, because the conversation should already be over and you should have the vest on, which means even if you do get shot things will probably go better for you and you now have the mental energy to work towards not getting shot.