I can read datasheets perfectly well, and Arduino seems pretty good by the low standards of microprocessor programming tooling.

I mean, you can program in C rather than assembly language! And you don't have to pay £300 a seat for the compiler! It works on windows, linux and mac instead of being windows-only! If you open source your project, other people can contribute and they don't even need a £150 tool to download the program to the chip! Other people can compile your code and have it work without needing to know the details of 'linker scripts' and 'codesourcery toolchains' and all that stuff!

Maybe, but this (often buggy) closed source stuff and not having a proper data sheet causes a lot of trouble for projects creating these nice firmwares (micropython, nodemcu, …) which people tend to use.