there’s a good reason to use the proper shading model and textures, it’s just sometimes not worth it. And if you know that some value is always the same (or just a fixed value over all pixels) you end up having a single grayscale texture channel you could perfectly use for something that’s really worth having as a texture channel (e.g. I prefer having a roughness in texture instead of specular, if I really need to decide. Specular can often just be a single static value, having the default value is good enough in most cases).
The graph you posted looks reasonable to me. You probably don’t want to reinvent the wheel here, but understand what’s happening in general (e.g. what SSS does and where it comes from etc). Of course it’s fine to use an existing material as is, but for simple stuff it’s often easier to just build it yourself (e.g. simple environment assets with only slight texture adjustments and some detail texturing. This can be like, 15-20 nodes in total).