Maldini and Lizarazu in that era were better than Carlos at LB, what he had over them was a more attacking game, but pure defending in that era they were better and they also were also good at attacking just not at the level of Carlos who was a winger who played LB.
Like i said FBs for the top teams today are not defenders they are winger/midfield hybrids, the game has evolved, doesn't matter if they cannot defend as you say, when they get 15-20 assists a season, its better than making 10 defensive mistakes in a season that lead to goals.
Look at Man United, 2 fullbacks cost a combined £90 million, last 3 seasons together they have 6 assists in the PL combined, you don't win things in the modern game with FBs with that output.