People keep on confusing Toneri as some full fledged Otsutski when he was like the rest of them a decedent, all be it with more inbreeding compared to the rest.
Momoshiki+Kinshiki was the only Otsutski that they killed. Kaguya they sealed and did not kill, let alone face her at full strength. If people think Naruto and Sasuke can handle an actual whole clan if they went all out, and not some trickle were they'll only send one dude after another, then you guys are overly optimistic.
Kaguya made the white zetsu army not because she feared Momo, he is more like the Raditz of the group before the real threat emerges.
Even if you make the top official just only Kaguya level (which is likely not the case) add 4 more people to this dude that are Momoshiki+Kinshiki level and have them invade and you got yourself a problem.
Naruto and Sasuke can't seal these guys since they aren't from this planet and are part of the 10 tails.