to me thats like saying Sharingan isnt MS. its just higher version of the same doujustu, or are you implying the sage of six paths couldnt use genjutsu as well as an uchiha? It just that in the current era of the naruto world you need both Uchiha and Senju blood to awaken it since both uchiha and senju blood has become diluted over the years due to the infighting between the sages sons which lead to the creation of two clans in perpetual war thus leading to the dilution of their original blood line power and the creation of the sharingan(a downgraded rinnegan). To support this view I present this scan of the manga stating the son that started the uchiha had his fathers eye's meaning rinnegan not sharingan
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heres a better close up showing the rinnegan in the uchiha ancestor
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i wonder if sauske banged tsunade or more realistically karin(as she is uzamaki like pain) if his kid could have rinnegan since he would be part uchiha and part senju ahahahahaha
Also madara hasnt been shown using rinnegan for genjutus becuase he didn't unlock them until was old and near death(no longer fighting), and after he did unlock them he didn't keep them very long as he transplanted them into nagato sometime before telling obito about him, as shown in the genjutsu flashback scan in my earlier post.