I don't think it assumes you are an IT person. Lots of non-IT people use it all the time. However, it is optimized to get the job done quickly and efficiently because......that is what it is for. The idea of architect is that someone has something they want to accomplish and it helps them do it.
The idea of Architect as a teaching tool is interesting but the problem with documentation like that is we are all volunteers and someone actually has to be motivated to write all of that documentation.
Additionally, you are talking about some fairly complicated topics. How to partition disks, the pros and cons of choosing all the various filesystems, considerations around LVM and decisions on what/how to encrypt are lengthy topics that are difficult to summarize in a meaningful way. That is just the topics from one section of the menu.
Other decisions such as which DE to choose are solely a matter of personal preference and there very few legitimate pros/cons.
When you put all that together, you are ultimately asking for someone to make a fairly substantial investment of their personal time to pull all of that together.
That being said, if this is a topic you are passionate about, why not take the project on yourself? Nothing that you select in the installation process takes elite technology skills to understand. It just takes the patience to learn what each thing is. For the most part, that documentation is already out there in various forums and is not Manjaro specific.