Only have 2 kids myself, but did grow up in a family of 4 children and I loved it. Never felt my parents didn't have time for me. Often shocked and saddened when I read on MN that of course it was normal in the 60s, 70s and 80s for parents not to want to spend time with their children. Not in our family it wasn't. We had great games and great adventures and I never felt I couldn't have 1-1 time. Two parents, both equally engaged with the family and equally hands-on. Nothing they enjoyed more than talking to us or teaching us or just spending time with us. (When I say adventures, I mean little ones: sheltering under a coat in the rain, eating our sandwiches in a bus shelter, making a den).
We didn't have a telly, but plenty of things to do: diy, cooking or baking together, listening to stories.
I did wear my brother's hand-me-downs but very much preferred that to my mother's idea of nice girls' clothes. Indeed my own 2 also wore hand-me-downs and second-hand clothes: I think it's a dreadful idea to throw away functional clothes just because they're not brand new. I am wearing my late mother-in-law's clothes now.
Also didn't have a car so that was one problem solved.
They partitioned rooms off and slept on a sofa-bed in the living room so we could each have our own space.
Don't think our teen years were particularly stressful: the most stressful part as I remember it was my mother going through the menopause, which was actually a bit worrying; the rest of us had fewer issues. As for worrying about exams, that is partly to do with where I grew up, but there simply wasn't the competitiveness: parents were quite happy to accept that some of us might go to uni and some of us might not. In the end, it was an even split. Two of us did PhDs, one started out in a low-skill job and worked his way up, one set up his own business, very much on a shoestring. We've all done ok in life, just different paths.
Thinking it over, I wonder if the biggest part of the success wasn't that we had a dad who was full of energy and just as hands-on as our mum. People on here often speak as if children were mainly a thing for the mother, as if they are the ones who have to juggle and be torn while dads can just carry on doing their thing. I never experienced that in my own 60s childhood. My dad would pedal home as fast as he could at the end of the working day to cook family supper while mum mended our clothes or sorted the laundry; at weekends, he would be whizzing the hoover round and mopping the floors while she dealt with dusting and tidying. He taught us to use tools and ski (in the garden, not Alpine resorts) and map-read, mum taught us to cook and sew and knit (no distinction between girls and boys). When we went on (fairly basic) holidays, he would happily carry a child on his back for hours on end. I don't think I ever saw him sit down and rest while mum was still working, though the opposite sometimes happened when she was unwell. And yet I never remember him seeming grumpy or resentful. I don't think it ever occurred to him that there could be anything more fun than doing things for his family, or than sharing fun things with his family.
As for the carbon footprint, that was at least partly offset by our youngest sibling being adopted.
Do I think it is worth keeping families smaller now for environmental reasons? Yes, I do.
Do I think it is impossible to provide 4 children with a happy, fulfilling childhood? Clearly not. But I do think you have to enjoy family life more than almost anything else to make a go of it.