It is true that he went on to do crazy mathematics without any formal education but we really don't know what he could have achieved if he were well versed in contemporary mathematics or even had access to some advance textbooks.
It is also true, per se, that you don't have to be formally trained to make major contribution but I guess this really doesn't apply to Ramanujan. Being formally trained is one thing and being completely untrained is another. He didn't even have access to decent textbooks. He was starving. He had no mentor. It was his sheer genius which played a key role. Given his circumstances, I don't think any other ordinary person could achieve that much with any amount of hard work.