I don't see anything wrong with a smith machine.
I bet you could take 2 people with the same genetics. Put one on the smith machine only and the other one on barbell. After X amount of time I bet you don't see any difference between the two.
Usually people can lift more weight on the smith machine because the starting weight is less than a regular barbell. Some smith machines have counter weights, so basically the bar weighs jack shit.
... From a bodybuilder to a powerlifter