Momoshiki is definitely far superior to Kaguya this is mentioned
in the anime
Manga
Databooks
and countless novels
People need to understand Kaguya isn't god tier anymore, the further we get to the story the more we learn she was pretty much a criminal on the run from a Clan full of characters much stronger than her.
However
This doesn't make Momoshiki 5-A, as 5-A Kaguya was only able to get that via absorbing the chakra from the world. yes, its' true that all that chakra once belonged to Kaguya..it was also mentioned before that Chakra can be cultivated and grown so the chakra she absorbed is likely far more than it once was.
Momoshiki should be at least low 5-B via being superior to Kaguya.
Ok let's knock some questions some might have out the park
1.
Momoshiki 'doesn't' know about post eating Fruit Kaguya
A: Momoshiki makes it clear in one of the earlier episodes that the Clan has been watching earth for thousands of years, they know about Kaguya, Hogoromo ect, them not knowing about the fruit would just be insulting as they reference a shit ton of events, including the Last Naruto Fight.
2.
Momoshiki cant 'be' as powerful as Kaguya anyway as she ate the divine fruit',so' they likely talking about base Kaguya.
A: Doesn't Matter when Momoshiki has done the same thing...multiple times... in fact Momoshiki wiped out an entire civilization and the fruit that ate on that planet which also had a divine tree was merely "adequate this time around" implying his had more than one before
3. If Momoshiki was really that much more powerful than Kaguya then Naruto and Sasuke would not have beat him because they were struggling with her
A: Well they could have just gotten simply stronger since then?, Naruto is a Shonen..in fact it's a battle manga which falls victim to the power of escalation effect, where threats constantly get stronger and the heroes need to aswell to match them, if you have watched any shonen power manga that's not One Piece then you know what I'm talking about.
4.B
ut Shadow. Naruto isn't like other Shonen, they rely on abilities, not power.Naruto doesn't have power of escalation stuff.
A: Hahahahah...i think someone missed the last 40 percent of naruto
or the fact that Naruto's base mode went from town level to small country level in two years.
5.
But Shadow Kurama stated that Naruto got rusty
A: He was talking about his Battle Awareness... your chakra cant get rusty.. ev,en so, everything that we've seen is contradicting this statement anyway... base naruto was able to for a few seconds keep up with Momoshiki anyway, Feats>Statements. also there is the fact that Kurama could have just been pulling Naruto's Leg as later on Naruto says the same thing to kurama, its friendly banter.
6.
But Naruto got stabbed by a sword ,he must be weaker.
A:Ohh you never heard of the secret Ninjutsu ability called plot no power no jutsu?
In conclusion Momoshiki is indeed more powerful than Kaguya but doesn't scale to her 5-A feat as that feat was done via absorbing everyone's chakra, while you could say that Momoshiki has eaten far more fruits and could have more Chakra than Kaguya but as we talked about before that Chakra doesnt always mean AP, its a case to case basis thing and ontop of that it would lead us to more speculation than i like as speculation can lead to inflated results and scaling
