Hi Todd: A very oversimplified answer.
I see the recipe for non-evangelism consists of these things.
Our culture is growing more and more aggressive to dissenting opinions, there is a lack of public decorum and a real lack of internet decorum. So when controversial issues are brought forth, the response is an attack or disinterest or disdain toward that opinion.
Stir in briskly a mixture of cowardice and fear, here the Christian knows he may be attacked or reproved for sharing his faith to friends, strangers of work-mates. At best he/she is considered 'odd' and now instead of friendliness there is a coldness.
To solidify this mixture you sit under preaching that has no evangelistic zeal, it resists giving any urgency to congregational street preaching, confrontation, theological confrontations, conflicts in cultural trends. The idea is to continually make Christianity to be all about self, what can do to improve self, marriage, kids, finances, jobs, friends, morals, disciplines. It's all inward focused.
combine all of these in various proportions and you will get a quick-set cement that kills zeal, quenches passion, questions sacrifice, repels overmuch righteous thinking or living.
All of this is for one great purpose, to end zealous passionate evangelism. The best Christian Churches have no prophets to correct, no evangelists to make the urgent calls to repent, no sold-out Pastors expecting their congregation to minister everywhere, anytime with only what they have.
It's not just about a deficient gospel, its a deficient pulpit, a deficient holiness in the congregation, a poverty of spirit devoid of any desire for the salvation of the lost.
Remember what we've all been saying in here...No evangelistic service on Wednesday, no intercessory prayer for the lost, no interest in ministering to your neighbor or stranger at the mall, no bible studies focused upon going from pew to a neighbors porch.
Young churches are all about babies, kids, doctrine, friends, potlucks, movies together, beer nights, bowling, superbowls, baseball at the park, hobbies, date nights, kids birthdays, girls night out, mens retreats to go to a place where you will not need a bible.
Any of this sound familiar?
I consider this recipe a workable and obtains observable results that can be measured...Satan himself is the Chef and his princes see to it the ingredients are apportioned to every congregation in our country.