You're forgetting one major variable in the equation. Kids grow. It was so hard when Elena and Chloe were little. Even though I only had two kids; I had no helpers. Now I have seven at home and 6 of them are helpers. Four can do almost everything I can do. And they don't groan when I ask them to change a diaper. They fight over who gets to.
While I'm nursing and cooing at my baby, four kids are doing their school work independently. (It's not all independent, but it's not all 1:1 either, like it was in Kindergarten and first grade.) I take a nap every afternoon while Julia, Daniel, and Lydia are napping. While we're all napping, the four big kids play games or "house" together. I couldn't do this when my kids were younger. My nap was totally dependent on theirs. Now, if they wake up, the big kids entertain them while I snooze on.
I don't have to figure out how to entertain two bored children while I grocery shop. I have six children who are getting groceries with me, while I read the list and keep the baby happy.
My life is easier now, not harder.