In fact, all four gospels connect John the Baptist with the prophecy of the voice crying out in the wilderness (Matthew 3:3, Mark 1:3, Luke 3:4, John 1:23):
The voice of him that cries out in the wilderness, "Prepare the way of the LORD. Make straight in the desert a highway for our God. Every valley shall be exalted, and every mountain and hill shall be made low, and the crooked shall be made straight, and the rough places into a plain." (Isaiah 40:3-4)
The phrasing is similar enough to teachings about exalting the humble and casting down the proud that we can take the hint: we're the wilderness. And when John the Baptist came, his work included teaching honesty and contentment -- not exactly traditional construction work for a road builder, if Isaiah had been discussing literal highways.
John's main work, baptism, also points to the rough places being inside us. The gospels record him casting down mountains and straightening out the crooked -- it's just that we were the crooked ones. To put it plainly, the chief obstacles to a smooth entrance for God are inside our own hearts and minds.
To be sure, nothing will stop God's kingdom coming. It's just a question of whether he finds us as a rocky desert or well-watered plain.
We are once again at a time much like John the Baptist's time. We are once again waiting for the Messiah to come. But Jesus sent his followers out to baptize and teach. If we are the ones baptizing and teaching, then we have inherited John the Baptist's job. It is our turn to be the voice crying out in the wilderness, "Prepare the way of the LORD. Make straight in the desert a highway for our God."