The PKM pipeline is :

Discovering PM solutions upon entering the workforce and deciding to use them for your personal life.

Shortcomings drive you to discover PKM software like Notion and Obsidian.

Picking either one or the other.

Switching from Notion to Obsidian or vice versa.

Starting to write your own PKM.

There is no class of software more entropic because everyone's requirements are so specific to the individual.