That's it, it can often be taken as criticism of their parenting, but when we know better we do better. We think back to how our babies were in car seats/carrycots/in the car etc and compare it to how our parents did the car, if they had one, now we look to what is available now and how much safer it is for children in cars nowadays. we did what was best at the time, and are happy to move on, hope this is a non-controversial example.
And yes, how a baby's gut develops, about allergies, which have always been a thing but often put down to fussiness, many other things, and I think it's a biggie, how a baby's mind develops. A good read on this is a book by Margot Sunderland, published both as The Science of Parenting and What Every Parent Needs to Know:, She is a top Child psychologist, who has worked with children for decades.
Another thing is that unless you are around babies and small children, people forget what really happened, and what it was like living 24/7 with a small person. It wasn't always how you remembered it, I know cos I was there. For example, it was regrettably not uncommon for babies to be given meds to make them drowsy, or as I once witnessed, whisky sucked off a finger. Someone I knew back then tried to persuade me to give a common antihistamine to my teething baby, now not allowed for such young children, I was aghast, no way would I ever do that, but I was told that most mums used it, it wasn't a big deal, well it was a big deal to me. Also, many parents have to both work nowadays, it did happen back 40 years ago when I started having babies, but not so common, so life is so different.