Yahoo Pipes didn't really offer that, or any anyonymous stdin/stdout. So huge graphs were necessary for complex problems.
But Yahoo Pipes did have submodules. You could have one of your pipes as a block in another pipe (I'm planning on supporting that at a later stage). And it had userinput that could get assigned as additional input to blocks in a pipe (for that I don't have a mental model yet).
OTOH unix-style pipes (also used in jq), shpuld be even more limited, being only a tree. They can get too complex, and then you use files as a way to implement modules (in a sense). So pipes have their place.
It is, which is why basically all graphical modelling techniques used for system analysis use it. An executable diagram system that doesn't leverage the experience of system analysis diagrams seems somewhat poorly considered.