I won't argue about laser circus and weighted boulder, because you're right, he does not have them. Those are just the jutsus I would want if I were him facing her.
But your other points:
Level scaling means nothing here.
The anbus of the leaf had to get together to do one FTG with Mei, but that didn't change the fact that they could do it. Kakashi has a kamui limit, but can spam it if he's being fed chakra by Kuruma and Sakura. And Madara may only have one or two Izanagis in him, but let him catch his breath, and he may squeeze out a third.
Naruto and Sasuke were already powerful. Naruto had traces of the tailed beasts in him from playing with them earlier and learning their names. Sasuke had EMS and was given Hashi-cells and sage chakra from Kabuto. Hagoromo only enhanced their powers by giving them a mode. Remember the mass FTG that saved the SA from the JTBB? Same principle.
Madara did not spam Izanagi because he was nerfed before we could see his full power and he was toying with everybody when he was an edo. And you still didn't address the Izanami issue. Izanami ends the fight if BZ is taken out first. Cheers.