I must say though that when my kids were little I could have looked after four or five by myself - I left teaching to childmind and I had three under 18 months nine hours per day from when my eldest was nine months old until my own dc2 was born. I absolutely adored it. When my 3 were all little-ish I often had a friend for each over and was happy as a pig in muck with six kids under seven in the house. So if my body had cooperated (a fourth pregnancy would have been very high risk for me) and we'd had unlimited money
I might have been tempted to go on and on... I was bloody good at wrangling toddlers and preschoolers.
TBH if I'd had a huge brood I'd have struggled to give them all the individual attention they need as older children and teens. I don't buy into the "teens are so difficult/ more work than toddlers" narrativeat all but they do need very individual head space from their parents - older children and teens need to be treated as individuals - obviously little ones do to, but usually a big brood of tinies have more in common and more similar needs than the same individuals ten years later do.
Teens and older children are time intensive in terms of running them around, solving sometimes complex problems, listening, teaching life skills, complicated homework and organisational help, more driving them around
and expensive in terms of driving lessons, vehicle insurance, school residentials, sports equipment, petrol costs, big cars to fit adult size early teens into, orthodontic treatment and never ending adult size shoes during growth spurts
Obviously a lot of that is luxuries, but not necessarily something people think of if they're really enjoying a big family while the children are all still tiny.
Juggling the needs of a large number of teens and pre teens close in age would be incredibly difficult to do well, I suspect.