At least Mc Carthy thought that machines from the 70ies should have enough power to do it, i.e. it is an algorithmic/representation/etc… problem, not a lack of computational power one.
If you look at what happens in nature, relatively low-level organisms are capable of some traits that we wish the most powerful computer had (vision of insects, etc…). Also, if you look at a well defined problem like speech recognition, the relationship between computational power and say accuracy is closer to a logarithmic curve than an exponential one. The law of diminishing returns has been the rule most of the time.
If you look at what happens in nature, relatively low-level organisms are capable of some traits that we wish the most powerful computer had (vision of insects, etc…). Also, if you look at a well defined problem like speech recognition, the relationship between computational power and say accuracy is closer to a logarithmic curve than an exponential one. The law of diminishing returns has been the rule most of the time.