Well… you do realize that all those monks had the nikayas memorized and they recited them in group every day ?
It is not distant learning like now days.
It is not possible to go straight to Sutta and learn.
While Buddha was alive, he created most of the suttas and recited them daily with the monks. Did he leave any recommendation that 1 generation after his death, people should start writing new books and add them to the suttas ? On the contrary, he left recommendations not to do that. And it is good that early Buddhist schools put their new ideas into abhidhammas and did not corrupt the nikayas too much.
It is like trying to learn English by reading the dictionary. (This is what I tried to when I was young because I did not have a teacher).
I would say the dhamma is more like learning biology or chemistry. To do it good, we need a good manual such as the nikayas. Learning pali is like learning English.
And how did that teacher become so well knowledgeable in the suttas ? How can one ever become like a teacher ?
Another problem with the abhidhamma is: witch of the 6 abhidhammas is correct ? Theravada is the school that survived, but how do we know the abhidhammas of other schools were wrong and the Theravada abhidhamma was correct ? They all claim to be perfectly in line with the nikayas…