Joseph, I’m glad you think every Jewish family should have many children. How do you define “many”? The mitzvah in the Torah is to have a boy and a girl.
My Rav told me that R’ Reuvain Feinstein shlita told him that he wishes people in Lakewood knew that you can easily get a heter for birth control if needed. He said people there have a kid every year, when they can’t afford it, both financially and emotionally. I know from my brother that in Lakewood now, every chosson is told during his classes that birth control can be an option, and they need to ask.
I was also told that one of the big poskim in Lakewood (I won’t say which one, as some people might be upset by this) said that in the time of the Gemara, a woman’s body took longer to recuperate from giving birth, and wasn’t able to become pregnant for 3 years (not that she wasn’t allowed to for her health, her body didn’t ovulate again for that long). He said that nowadays, he thinks it should be mandatory for a couple to wait a few years between children, because they can’t deal with so many children, again both financially and emotionally.