Madara and Hashirama are a class of their own.
Normally senjutsu is too strong for the normal people to take. Without training, even a portion of senjutsu chakra (curse mark) can wreck your body as seen from the sound 5 and CM Sasuke, all of who were hesitant to go into stage 2.
Also, if senjutsu didn't require training Orochimaru would have had it (the problem was his body wouldn't take it), Kabuto wouldn't have to turn himself into a freak, Jiraya wouldn't have to train his whole life to gradually get more adapt to it and Minato would actually know how to use it (rather than being terrible at it).
Senjutsu requires quite a lot of training and natural talent to use. The only ones who mastered it fully were transmigrants wich had ofcourse special kind of power to help them out.
Bringing Madara and Hashirama in (not to mention we don't even know how long Hashirama trained to aquire his SM) doesn't say anything about people in general.