Interesting points! I do agree that some cars are made to have a life cycle in mind.
ATF is sealed nowadays, and for good reason, one of such reason is keeping the moisture out. As ATF is hyper-sensitive towards water
Cars engine bays being more packed is an inherent design to improve weight distribution and add more technology (be it turbo, or electrical motors). Is it harder to service? Sure.
But technology moves that way, look at the lovely Nokia 3310, removable everything (from case to battery to buttons). If they were to do it for say iphone X, would the phone be 1 inch taller and 1 inch wider and carries a huge lip for future serviceability?
You are right that planned obsolescence is here. But, if you want a car to look good, and have all the tech and safety features you have today, price to pay for moving forward?
Back to ATF, yes, following the service manual is minimum (and recommended), should you want to change it at any mileage (earlier) would be better. Kinda like changing your smartphone batteries yearly, is it better? Yea, but is it cost effective? No one knows.
Honda ATF DW1 only cost rm25 a litre. Honda City will only need about 3 litre and Honda Accord maybe 4 litre. All in all, rm100 is enough to replace the ATF provided you DIY. I would say its quite cheap as a preventive maintenance.