>What's the point of having a progeny in a world that is going to hell ?
"The harvest truly is plentiful, but the laborers are few. Therefore pray the Lord of the harvest to send out laborers into His harvest." It's precisely because the world is going down the drain that we need as many Christians as we can have, and how else do you make new Christians except by evangelization + raising your own children as such?
>They will witness things that no one should.
Every individual has been witnessing something that no one should - death, and sin. Nothing has changed.
>Just to have more people in His kingdom ? Then why stop at 4, 5 ? Why not produce thousand of offsprings ?
Children are a gift of God. He decides how many you will have. Just don't go out of your way to prevent His will.
>Someone enlighten me on anti-natalism (or Nihilism as a whole) and Christianity, please. God bless.
Stop thinking in practical terms. Christianity is far from a "practical" religion. We only listen to the promises of our Lord Jesus and look forward to the parousia. Find a vocation to support the Church, and, through the Church, to heal the world - whether it is by getting married and having childen, by becoming a theologian and writing of our experience of God for the sake of others, by becoming a monastic, by getting a job that supports the Church, by becoming a lay ascetic, etc. - and don't think the world has more power than we do. Christ conquered the world.