The repair itself is just as easy as it has always been, perhaps you need some additional tools like a microscope, but that's about it.
The issue isn't the repair itself its getting the schematic/service manual/service software and the parts. Which is all artificial limitations on 3rd party repair.
The whole "modular repair" thing is not really the whole story.
Yes, it's cheaper/faster to hire low-skilled staff to follow a simple diagnostic flowchart and replace the entire PCB while the customer waits, rather than have an engineer fix it.
But a lot of the time the business will double-dip. The store will charge the customer the cost of an entire new module, which is expensive and has high profit.
Then every month all stores box up all the dead modules and ship them to one location where a small number of engineers do component level repair on them in bulk and turn them into refurbished boards for all the low skilled shop workers to use as new modules for repair.
Saves on shipping, only requires a very few skilled engineers, and you get to charge for the module twice, maybe even more times as you sell it again and again.
(I think this should be illegal, but that's another story)