Immersed In the Gospel

Whenever I read texts from Oswald Chambers or books such as Pilgrim's Progress, I'm amazed at how well these writings from over a century ago speak so well about man's current condition. There truly is "nothing new under the sun" and no temptation which is not "common to all mankind". Both man and Christ are the same as they were 2000 years ago. How has man not grown in Christ in the last 2000 years? We've had this long to study Him, to know Him, and yet we have not moved an inch! Is it because we refuse to be immersed in the gospel? Is it because instead of plunging even deeper, each generation moves even closer back to shore? Is it because we've dulled our taste buds for the holiness of Christ and instead of craving more, we're satisfied with less?