IMO this has nothing to do with both parents working full time and everything to do with the modern theories about bringing up children from birth to school-age.
I have lived in Denmark since 1970, a period of time that co-incided with Danish parents both working full time and having children who from the age of three months or thereabouts were in creches during their parents' working day and from the age of 3 in kindergarten.
Until around 1990, children of 3 were not allowed to start in kindergarten unless they were toilet trained. No-one thought this unreasonable and nearly all children were toilet trained at 3.
Ten years ago, when a young woman I know had a baby she was told in no uncertain terms by the health visitor when the boy was 18 months that she MUST NOT begin toilet training at that early age. She objected, as the creche staff were so over-worked that they only changed dirty nappies - wet ones were just ignored, so her child was sitting all day in a soaking wet nappy. But his mother was firmly told that no child can control its bladder before the age of 3, as the body does not produce the hormone that controls the spincter before that age.
This may be so, but my mother always proudly said I was out of nappies before I was eighteen months old, my younger sister most assuredly was, and her three children too, and none of us have been affected by the dire consequences of early potty-training used to scare young parents into leaving the matter well alone now until their children are at least 3.
Now we are seeing children in nappies at the age of four, which does not affect kindergarten classes in school so much here, as children are six or seven when starting school.
On the matter of books - there have always been children who started school unable to hold a pencil or ever having seen a book. This has little to do with the computer age as such, but much more to do with the level of literacy in the home.
If the parents' only reading matter are the local supermarkets' advert mags. you cannot expect their children to know what a book is - and there are still adults who never read anything, especially now, where reading newspapers is not an everyday matter - the news is heard or viewed on TV or online.