There is a fundamental flaw in trying to justify skill level in an activity by comparing yourself to the level of the entire population, the reason people see aotc or ksm as not being impressive is that it is something easily achievable within the playerbase that is actually dedicated to the content.

A heroic raid can be cleared with players that have poor understanding of their classes do not utilize their kits properly or do not understand the fights well. The same can be said for 15 keys, most people dont even learn the nuances of most dungeons until a much higher keystone level because most mechanics do not punish you enough at a 15 level.

KSM and aotc are rare within the entire population but for the communities that actively do these activities they are a mid tier achievement