I don't get your point. Atmega328p arduino boards start at $2 or so ($4 for uno) and are currently at "apt-get install arduino" level of convenience that arm isn't getting anytime soon. Plus the whole point of microcontrollers is in working against specific chip, not universal API.
You can get STM32 boards for the same price (Blue Pill/Black Pill). ARM does have 'apt-get install arduino'-level of convenience. You can actually use the Arduino IDE through stm32duino, which is literally a matter of adding an additional board manager URL to the IDE.
Moreover, you program STM32 boards (besides mBed, etc.) with Rust, which is also easily set up. The Rust embedded ecosystem is much smaller, but still nice for hobbyists. Moreover Rust with ARM cross-compilation is easy to set up.
Another nice feature is most ARM CPUs is that setting up and using gdb is trivial (e.g. with STM32s it's usually a matter of starting OpenOCD and then connecting to that with gdb).
mBed is complicated. Arduino is simpler for artists/hobbists.
The libraries of each are written for different groups of people, and it shows.
For example, you can do a lot of stuff in the Arduino without using pointers. The mBed requires pointer usage.
I don't think it needs pointers any more than Arduino does. Can you give an example?
nRF52 is amazing, but IDEs are a trap. Sure, use one for your first project, then immediately move on to a proper Makefile.
All professional development with microcontrollers is done with Makefiles, because of Reasons.
You know most IDEs support CMake and custom build tools?
E.g. ST Nucleo boards are around £10. Or the nRF52 device board is £30 - that gets you a proper BLE/Thread/etc board with a fully documented radio peripheral. You can write your own radio protocol if you want.