The Colts roster has sucked for 6 years. Polian kept giving all the money to Manning, one receiver, and one RB. He let the defense get really weak, putting about 70% of the money on offense.
It wasn't a story because Manning was just that good. He overcame those barriers and still won 12 games a season.
Every QB in the league can make throws. Look at Flacco last year. He isn't a H.O.F. QB, but when you have a good team around you, it makes it easier for the QB to get things done. And especially when there is a decent running game, that punishes the defense, giving the QB bigger windows to throw into by the 4th quarter.
Neither Manning nor Luck have had that luxury because they have had ZERO running game and a very substandard defense. This year Colts defense was 20th in yards / game and 9ths in points allowed. By contrast, Seattle was best in points allowed and 49ers were 3rd. The QB just isn't as important in those systems. I'm not saying those guys are bad. They are just not remarkably better than a lot of other guys, IMHO. But either of those guys behind center on the roster the Colts fielded this year and they get nowhere close to the playoffs.
But, that's just my opinion.