Where are these in the Blender world? Doesn't everybody want some basic materials to play to get going really quick as with Substance painter? Minumum needed "starter-pack" resources exist as CC0, yet
Blender 3D: Noob to Pro - Wikibooks, open books for an open world
Free Material Pack for Blender 3D # 101 - x3dRoad
Top 10 CGI Material Libraries for Blender | Vagon
Blender Market | A Unique Market for Creators that love Blender
Top 6 Websites for FREE Textures and Materials (PBR) - YouTube