what you see there on the real looking tree is a bunch of techniques combined. Subsurface scattering is not a magic solution to make it look real :).
For realistic results you need to know how to make textures for all channels (albedo, specular, normal etc.) and then apply subsurface scattering.
Best is to follow a ton of tree tutorials on youtube.
Side note, Your tree branch model is also flat. You should enable two-sided material for it and create a custom normal model in the shape of the tree (spherical) to make it look fluffy, else it will look very 2006 anyways.
Standard normals:
spherical normals (fluffy look):
