Not true for MacOS, though Apple is not exactly going out of the way to make it easier. Closer to the truth for iOS, where all "advanced user" stuff is not only not made available - but applications making it possible are explicitly banned. I know there are reasons for that - like if you can do power user stuff, you probably can circumvent Apple restrictions that bring them that juicy 30% payment cut - but the fact is the fact.

However, this is the iOS picture, on Mac picture is much better - I could do on Mac almost every power user thing I did on Linux, albeit I'd have to do more research to find the proper docs and the proper tools, and some of the tools may be not free (in either sense).