I started with a small MySensors project more than 4 years ago and life was easy then The choices were few and I felt they were well documented.
I began with an Ethernet gateway but moved to MQTT (ESP8266 because of WiFi) once it was available. The choice of radio was easy and even if there were problems most could be solved. I still run 10 - 15 items using NRF over MQTT to OpenHab and also have quite a few Z-wave items connected to this system.
Today there are heaps of choices and the development continues but my feeling is that MySensors is still mainly driven by a small community of enthusiasts working on this on their very limited free time. As more and more functions/variations are added the complexity grows and the need for correct documentation increases exponentially but the resources are not at all growing in same pace.
I have some experience with using much larger projects (OpenHab, ArduPilot, PX4 etc.) and and also here documentation often is a mixture of updated and outdated info. Many times the forums are where the correct answers can be found but very often there are many erroneous answers per one correct one.
For a project like MySensors I am convinced that the only way to go is to select an entry level configuration with few well working choices which are always kept alive and up to date.
As users become more and more experienced they will have come across a lot of useful info as well as have learnt how to find more. Hopefully some find documentation so important that they are willing to contribute also.
For the advanced stuff of course there should be an ambition to document it well and keep it actual but why not accept this as playground for the advanced users who know enough to find the answers as well as are able to assist others.
Last but not least. We always get what we pay for, don't we To keep a full blown MySensors activity well documented will cost a fortune and require very up scaled resources.