“Perhaps they shouldn’t get married if they cannot afford it.”
That is why there was a year separating the kiddushin from nissuin. You need to have a house and a parnassah before you get married.
Of course, that was the halacha then, I guess halacha changed.
BTW, many of the issues regarding birth control is sociological and not halachic. After the Holocaust, many people feel that to even mention birth control is assur. But like we saw what R’ Feinstein said (and others), it’s not 100% assur and people should realize that having 10-15 kids is not necessarily the best thing.
Keep in mind that even only 100 years ago, the odds of a kid reaching one year old was very slim. People had kids to replace kids that were lost. Today, with the advances of medicine, perhaps we should rethink this.