Argentina have improved their game a lot in the recent times indeed. Messi is still a big help for the team of course but they have many really skilled players in their squad right now. Their performance in the qualification round for the World Cup has also been mesmerizing. They made Brazil big difficulties in their game there. When it comes to a finale between Argentina and Brazil I must indicate that it would be great. But this would feel like a Copa America finale at the same time. 
So I think it would be better to have one of these teams playing against a European team in the finale.
Argentina did appear extraordinary in the world cup qualifying event for the Latin America zone, not only that they also managed to lift the Copa America as well as become Lionel Messi's first trophy for Argentina, but the world cup was not only represented by CONMEBOL but consisted of several continents in the world. , and we have seen the previous edition of the world cup where many CONMEBOL representatives often struggled against teams from the European continent and I firmly believe that the European zone will again dominate the Qatar world cup this year So I think it would be better to have one of these teams playing against a European team in the finale.