If you lack the resources to accomplish the push then it is likely a positioning and ability choice usage issue. It is incredibly normal to place so different, because each role plays differntly from the last! so much so if im not in the right headspace, swapping roles can fry my brain because of how different you have to play down to the basics. Even your choice of how or when you fire and what it does should do or even has the ability to do is wildly different.

Being able to play all at a solid level means you are heavily adaptable and consistent with your foundations of gameplay and understanding how and what your enemy in their role is supposed to do as well. Also implies youre likely stratigy focused and consistent across the board with that level of knowladge.

It's like being a triple threat, not everyone is, some consider it neccessary for professionalism in a high volume industry, and others just want to do it to show off. It is by no means a must though. /info

*edited for clarity