Chakra is the moulding of Shintai Enerugī and Seishin Enerugī gained from exercise and experience. Hagoromo is the individual who discovered the mechanics of Chakra and how to manipulate it to actually cause an effect and then proceeded to teach his findings to the world along side his religion as Ninshū, the foundation of Ninjutsu. Simply having exorbitant amounts of Chakra doesn't equate to being omnipotent if there is no way to actually utilize the material.
The Bijuu are the Jubi's Chakra. If the fruit was a little less potent in composition, it would still have given Kaguya some power. The Correlation does not match up with Naruto concerning the Chakra he received form the Biju as it did nothing to enhance his battle capability, power, ect. It's purpose was to extract that Biju from Obito. The Bijuu entrusted the power to dissect the Juubi to Naruto.
Why the vague speculation? If we are to compare Madara currently to the world in Kaguya's time they would all be "fodder" compared to him. There is nothing canonically stressing on the extent of Kaguya's power.
The Uchiha Stone Monument records that Hagoromo dissected the Juubi on his death bed and chose a successor which only imply's that his many creations and utilization of the Sword of Nunoboko occurred prior to that time. I would like to know your honest opinion on the matter, Byron123 . After witnessing Hagoromo wielding an Inyouton khakkhara while facing the Juubi as well as being a witness to what the Jubi is capable of while lacking the Hachibi and Kyuubi: do you actually think basic Ninjutsu, Sennin Modo and large chakra pools would be sufficient to stop the complete Juubi?