Experience is an important factor for sure. But in Argentina vs. Croatia, many players of Croatia and Argentina are very experienced. Messi will push his team for sure, it would be amazing for Messi to be world cup winner and he'll give everything for it. And we should not forget di Maria, who'll most likely come into the game 2nd half at least, or even first half already? We don't know yet.
Of course, Modric will try to give everything, too. 
Perisic and Kramaric aren't bad as well and Croatia has shown multiple times already against Brazil, Denmark, Belgium and Japan to be successful.
I'm expecting an interesting game, probably very tactical but could also be a game bringing us lots of goals, if one team scores early.