Personally, due to having recently built my house, I could never ever buy an apartment. The shoddy work, like you have mentioned is definitely not worth the money. However, if done right, this type of material use is definitely not just for temporary construction. Of course, this being India, construction standards aren't enforced properly. All these drywall boards come with specific gyidelines for constructing the frame, which, like you pointed out, seem to have not been followed in this case. In US, the joists cannot be spaced more than 16 inches apart.
I don't get how people can just hand over 3.5 cr and not get all details beforehand in written. Even for the simple 30L construction we recently got done, all specifications were mentioned beforehand including brands etc.
P. S. - Even in US, the bathrooms are constructed with drywall. However, they cover that with waterproof membrane and then tiles.