I repair many apple devices, few MacBooks though (our senior tech does those).
iPhones 5 through 8 plus are easy fixes in many areas. Screens are a breeze Batteries are easy to replace, just have to be careful not to puncture. Both front and rear camera are easy, as well as chargeports. The camera flash assembly is a bit painful as you have to remove mother board and gut out the phone to replace the cable that holds flash, mute slider, volume and power button. Small stuff like ear speaker is easy too.
Newer iPhones like X, Xs Max, and XR get a bit more complicated for screen replacements, but they are doable. Battery replacements are not too bad.
As far as them getting better repair wise, it's been pretty neutral.
Apple intends to fix certain parts of phones so they have to make it repairable to some degree anyways ya know. But at the same time they always give people used/refurbished phones when something manufacturer wise is wrong with your device, so maybe repairability will get shittier in the future. Who knows.