The argument "oh but the Soviets lost" is hokum, because they might have won, if they had been prepared to invade all the safe-havens, and the Mujahadeen were in pretty dire straights till they got US funding.
This implies that the Soviet Union would have had to invade Pakistan in order to win the war, which means they had no chance to win at all. Somehow I doubt invading FATA and Baluchistan would have ended the insurgency --- instead it would have simply continued in even more intensified fashion from Punjab and Sindh, with all of Pakistan drawn in as opposed to just the ISI. The whole of Pakistan would likely have been radicalized as a result.

Never mind the diplomatic and Cold War implications of another Soviet invasion of a sovereign country after Afghanistan. The Kremlin chose wisely to avoid this.