In fact, USSR was very competitive in most domains until ww2, and in fact, the ability to conduct dramatic changes at an insanely high pace is probably the biggest strength of a centrally planned economy (though if the underlying idea is bad, then the change become literally dramatic, see the great leap forward).
What made the USSR fall behind was the cold war, meaning very little foreign trade and too much emphasis on military (and in the end, the gerontocracy, with people in charge all being too old to do anything, but this is related to their dictatorial nature, and not to the central planning).
What made the USSR fall behind was the cold war, meaning very little foreign trade and too much emphasis on military (and in the end, the gerontocracy, with people in charge all being too old to do anything, but this is related to their dictatorial nature, and not to the central planning).