The problem with adding more communication options, as I see it, is that any more specific option they could add will be completely redundant at a higher level of play, because people were already doing that without the d-pad. For example, I used to really want callouts specifically for when to push forward or fall back, but as I've gotten better, me and my soloq teammates do that without needing the d-pad. And when we do need it, this way works just fine.
The beauty of "this way" is that it is vague enough that it's useful at every skill level. It can just mean it's time to push now, or it can mean "let's pinch this guy over here, he's all by himself", or it can mean that I have 7 clams and can you please throw me another one.
It is somewhat limited, but I think any more complex system would be too complex to realistically expect people to be able to use and understand quickly in game, especially when considering all the different skill levels it would have to account for.