The problem with the question is framing religion as exclusively Christian.

Islam is growing quite steadily and some religions are culturally based like Sikhism and Taoism as examples.

There is plenty of point in religious belief if that is your societies presenting coherence. No different to Liverpool and Everton. Cross cultural divides are social dynamics and will always exist as a part of our deep-rooted tribal heritage.

I suggest possibly the mega churches have a substantial following and that is where the younger people go. Possibly because of a magpie mentality attracted to the charisma and pretty boubles of pastoral ministry.

Give me the bells and smells of High Church any day!

Fear of reality is the main recruiting tool that religion remaining in its box of tricks and illusions.
However more and more people have ceased to fear the idea that death is the end, even religious people find the traditional idea of heaven to be silly and the threat of Hell despicable.
Mainstream churches are complaining that their congregations are dying off and young people are not coming in to replace the oldies. Though people in their fifties and sixties will claim a belief in god, most only attend church for weddings and funerals and christenings are becoming rarer as parents decide to leave baptism for the children to decide on when they get older.
Religion is fading in the west (except for in parts of the USA) because desperation and poverty are fading in the west except for in the USA, it is no coincidence that people turn to god when there is no medical and welfare system to turn to and where losing your job can mean your children may die from a treatable illness but you cannot afford to pay for the drugs.

Some people are just afraid to think they don’t have a sky daddy to watch over them and an afterlife where they’ll see loved ones again.