Momo does not have techniques on Kaguya's level. He has Chakra blasts, basic elemental jutsu, chakra weapons, black rods, elemental beasts, and chakra absorption.
These moves simply pale in comparison to dimension-shifting, chakra arms powerful enough to one-shot perfect Susano'o, perfect control over nature, infinite Tsukuyomi, Juubi transformation, chakra absorption (both can do this), ash bones that deal unhealable damage, dimension-busting truth-seeking orbs, and frankly far greater strength/speed.
Kaguya tanked even the nine Bijuu-infused Rasenshuriken. Momo was actually killed by a large Rasengan. I honestly highly doubt that the Rasengan used was more powerful than, say, the one Naruto/Minato used while in Bijuu Mode against Obito.
Momo was a "threat" to Kaguya in the sense that he was the one being who could steal her precious chakra fruit and gain equal or greater power. However, he never attained that power, or anything close to it.
Momoshiki was outclassed by a Bijuu Mode / Susano'o combo. Naruto didn't even have to enter his Ashura Mode avatar and get truly serious, and Sasuke only used Susano'o, swordsmanship, and teleportation.