Some children are naturally easier and more compliant than others.
Some parent/ child personalities click easier than others.
At a generational level, parents today are less likely to have learned parenting through being in large families with siblings, cousins and unstructured time in the community so it feels less instinctive.
There is more pressure that children must always be supervised so parents are either "on" or children are in structured activities. There's a lot less time to let children be, and let them come back to you. The community has lost its role in sharing the load.
Parenting has become more idealised. There have been manuals for a long time, but social media has changed it from reading a book for advice to creating online communities which can fall down purity spirals. About 15 years ago I got into "baby wearing" and joined groups to support the practicalities of doing that, but the groups became echo chambers of "attachment parenting" and fixated on minor details and unrealistic standards. I tended to spectate with amused detachment just wanting to look at pretty wraps and use them safely, but they can ceeate a damaging culture if people get too drawn into the cultiness of them.
Society has less space for children to learn by trial and error. The curriculum is very formal and rigid. Formal testing is taken seriously from a very young age, and qualifications at 16 have more impact on career opportunities than they once did.
Mothers in particular have more external pressure, particularly if they're trying to match equal career progression to men. Paternal expectations have shifted less on making equal home/ work expecrations.
There's no great halcyon era but I think that lack of experience and higher expectations are quite recent challenges that many parents can struggle with today. If parenting doesn't come naturally to you, there is a lot less slack, but that culture also tends to come from intending better outcomes for children.