The problem is that writing all these shaders takes a huge amount of time and work even for "experts" and therefore they don't want to give it away for free - if they ever finish it
Even with all shaders some indie would like to have, imm' not sure he will make and finish a game using them
You need a solid base : 3D models, great textures, level design (just look at Guild Wars 2 worlds) , characters , animation, 3D effects, good ideas etc ... Shaders are only put on top of that to bring candy visual stuff.
If you have bad textures, bad levels, bad characters, well ... shaders are useless.
Some other Engines bring to you a library of complete shaders, others propose some shader editor ... some are affordable , some expensive ... some for 3D artists ...
3DGS have a good shader base ready to make little next gen looking levels. It's to people to work