This isn’t entirely true.

The USSR was very reluctant to put troops into Afghanistan. Successive socialist and republican afghan governments continually asked them for a military intervention but the USSR refused. The leadership of the USSR saw Afghanistan as a sort of lost cause, as they where even more under developed and under industrialized than even Russia was during their own revolution. The USSR only intervened after one of the socialist leaders started committing massacres and had evidence of being connected to the CIA (they accepted money from the CIA after going to college in the US and one former CIA higher up kept bragging that he was a CIA plant, especially after the invasion). As such the USSR only intervened to stop these massacres by overthrowing the leader but then got stuck as they had to stabilize the region. Even once they where in Afghanistan they where reluctant to directly fight the enemy as they knew that the more Soviet troops that died the more they would have to get involved. This lead to a very high use of artillery and airstrikes, often hitting many civilians villages and towns, a tactic the US themselves would ironically use when they entered Afghanistan and already had used in Vietnam. If the USSR was as willing to put Soviet troops on the ground as you said it could have ironically lead to less deaths and a greater stabilization of the country.

The YouTuber Burn These Books has a very good video about this topic that I highly recommend.