The failure of the campaign comes down to a few things. 1) Supplies 2) Strategic position.

Both sides were fighting near and in mountainous territory that made it difficult to move armies and supplies. This favored Wei in defensive battles in which they were able to outlast Shu. However, even in situations where Zhuge Liang had a huge advantage, such as against Hao Zhao where he had a huge numerical advantage (about 50,000 vs 1,000) Zhuge still failed due to excellent defensive tactics and eventually lack of supplies which forced a retreat.

While Zhuge Liang was able to have minor victories across the campaigns (Jiang Wei defection, killing Wang Shuang/Zhang He, defeating Sima Yi's offensive at Hanzhong), he didn't capture any major territory that could make anyone consider the expeditions a success especially since the goal of the expedition was to capture Chang'an of the major Wei cities and a stepping stone to Xuchang, the Wei capital.