The construction and infrastructure boom in China over the past few decades suggests major projects can still be completed rapidly, even in spite of widespread corruption.

Political will can be an important driving force for pushing through major projects, but the most impressive feats of engineering are seen when there is substantial pent-up demand in an economy that can suddenly be supplied, usually due to social or technological change.

I think major projects could still be completed quickly in developed economies if the incentives were to align in the right way, but we don't see it often because the low-hanging fruit has already been picked.

India and Africa are probably the places to look to for rapidly completed major projects over the next few decades, and perhaps we could see significant industrial development in space at some point if the economics works out.