There are three broad categories of dissatisfaction with the mainstream secular world view:
1. The self-refuting nature of relativism.
2. The arbitrariness of ethics without religion.
3. Hopelessness and alienation.
Hopelessness and alienation are the hardest to identify and pin down, and are always deniable - but maybe they are the most damaging aspect of the modern malaise because - on the one hand - they render the individual unable to stand firm and make an effort to escape their situation; while - on the other hand - they lead the sufferer to escape his existential loneliness into distractions and intoxications (especially sexual) which take him further and further from the truth and from virtue.
Christianity solves all these problems; and that should be enough to recommend it conclusively when someone has nothing coherent or motivating to offer as an alternative - yet clearly this seldom happens, and conversion is typically a drawn-out process that is easily derailed (certainly it was for me).
What happens is that each Christian solution to each class of problem is met by a change of ground and criticized from a different perspective - so that the cure of alienation is met by the charge that Christianity is a made-up fairy story, while the cure of Christianity offering a coherent truth is met by objections that this system is immoral (according to modern secular norms); yet the grounded ethical system of Christianity is said to be arbitrary or alienating.
Such objections can go round and round without termination for weeks, years, decades...
It seems very difficult, in a world in of cognitive fragmentation/ specialization, to bring matters to a point - to force a total-world-view confrontation between Christianity and mainstream secular Leftism - a confrontation which Christianity would immediately and easily win.
Modern mass media culture, the partial professional cultures (e.g. politics, law, science, the arts), the weakness and wickedness of the human heart, and the cumulative corruptions of purposive evil at work around us all conspire to prevent such a confrontation.
But this is the great latent strength of Christianity. If, or when, a person brings themselves or is brought by circumstance to the point of balancing Christianity against secular modernity - and can hold themselves or be held at that point for more than a moment - then there is no doubt of the outcome.