[kaiusbrantlee]

re " how big the niche "technically literate to run their own e-commerce business, but selling on Amazon for other reasons" is,

As the platform matured, the level of technical literacy could decrease over time. e.g. the more technical aspects get abstracted away from the users.

Furthermore, users who are motivated enough would begin to extend their technical reach by means of self education, and/or collaboration with more technical party/(ies).

This is a common arc in technology.