No, obsolescence comes from having your role replaced by something else. Infantry should be obsoleted since WW1 thanks to invention of machine gun. But it is no

No, obsolescence comes from having your role replaced by something else. Infantry should be obsoleted since WW1 thanks to invention of machine gun. But it is not, because there is nothing to replace its role on the battlefield. Yet at the same way, you don't see horses on the front. Because they were replaced by combustion engine.