I ask you to figure out how to build a house, cook a meal, sow a crop by *not* distinguishing truth from
falsehood, by not caring to know what is real and what is not.:
Try this reveal the idiocy of crying out against reason.
*The problem is not reason itself but a society which has elevated reason to almost mystical status as the provider of answers and the ultimate solution to any problem.
Reason can be very useful, especially in the kinds of examples you use where a simple right and wrong are posible but reason is not the only human faculty which should be taken into account. Humans have emotions and irrational desires which can be just as important as their ability to reason.
The problems arise when we try to use rational systems exclusive of all else to solve problems. This is what 'economic rationalism' does for example.
Because its proponents claim that it utilises 'reason' they can come to hard and fast solutions to any problem and be absolutely certain of their success. Anyone who questions their orthodoxy is ridiculed as irrational and stupid. Opposition doesn't stand a chance in the publicity war because those who claim to be on the side of reason have automatically claimed the 'moral' high ground. 'Reason' has similar power in the human imagination as 'freedom'. Whoever is first to claim the term automatically wins the argument.
Reason is seen as an inherent good. If the system is rational it must be good, no matter what its outcome. It's exactly the same situation as in the middle ages. Whoever could be the first to convince that they were on the side of God automatically won the day no matter how successful their systems or ideas were.
I'll just make an observation on one of the examples you used. If people were purely rational whenever they built a house then every house in your town would look exactly the same. I'm going to assume that they don't. This is because of the multitude of irrational beliefs and desires which every human being has.
What happens when pure reason is applied to the issue of housing? Housing estates (you might call them projects).
The reasoned approach is that there is one identical, perfectly rational answer which can be applied equally to every homeless person in the city. The result? Hated by all involved. But the government departments continue to repeat the same procedure in response to every problem.
It's the same story in the military and economic spheres. I could go on all night but I won't.