I don't think it's too old, but I don't think it's ideal, either, in many circumstances.
As a disclaimer, I had a child at 40. It was great and I'd certainly do it again. By the time I really was ready to start thinking about another child, we realized our son was going to have challenges that required our money, time and effort. So that completely changed the equation of trying to have another.
But the truth is, although we are overall healthy, we are starting to have some health conditions. And we can see friends our age having severe conditions...or even dying. This isn't something that happens often in your 20s and 30s.
I do think consideration should be given to the fact that a child deserves two healthy, active parents. And while there are no guarantees, this is probably more easily provided if you are closer to 40 than 50 when you have a child.
Also totally don't get the argument of having a child/ not existing. Does that mean every couple should have 10, 20, 30 children? Sounds like a quiverfull mentality to me.
Another consideration is they are finding more trouble in children whose parents are older. My mother was the last of 8, born when her parents were older. And she was bi-polar -- the only one in the family. It didn't show up until she was in her 40s.