Di Maria I counted as a forward. Mascherano is a fantastic CDM but he gets played as a CB most of the time now. Cambiasso is old and overrated. Argentina are really not that good. As for Germany, Mertesaker is piss poor (and not a wing back). Shweinsteiger is fantastic yes, but the other names you mentioned don't matter as they internationally retired years ago... Gomez is experienced, Podolski doesn't start that much anymore. Their foundation is ALL youth.
Spain have Fabregas, Mata, Isco, Thiago, Busquets, Rodrigo, Alba, and MANY others (which is why they are leaps and bounds ahead), they win the U21 competitions a lot. They have such a fantastic youth system to step into their places, trust me.