I'm pretty sure this is the issue, believing that they created everything in the Cosmology with that Genesis statement.
But by focusing on what the story tells us, without theorizing as you have said, they rely on the Cosmology to have been created.
So since we have established the meaning of Genesis:
They take it to be planetary as this has a more consistent portrayal in the verse (while some people here see that planetary is too consistent, and that he should be way higher, hence they randomly chose universal), the highest is illogical (requiring them to have created the previous universe you assume they may have come and where they ascended to, literally everything according to the Genesis the opposition is trying to align with) & there are no solid connections showing that it refers to a universe instead of a galaxy, planet or an English-speaking region.
The original justification relied too much on this Genesis statement tbh, I'd be more comfortable just not scaling it, until it is elaborated on in the manga.
Look, your argument is merely a narrow perspective.
We are not always meant to be mere observers who rely solely on formal and visual feats. This is precisely why statements exist. Therefore, I believe you should clarify the core of your critique, as there is absolutely no issue with using statements as long as they are not debunked or contradicted by the visual narrative. Many well-known verses, despite having visual feats only at the planetary level, have been scaled much higher based on their official statements.
Thus, I see no flaw in using statements as a basis for feats; your reasoning on this matter is not convincing. However, your concerns that the story might eventually show something to the contrary are understandable. Nevertheless, until such a contradiction occurs, these statements hold immense value. This is not a flaw in the storytelling; rather, these are the story's "mysteries" to be uncovered in the future. As long as they are not disproven within the narrative, they remain completely valid.
Now, setting aside the validity of statements, let us address your claim that the "creation of the world" refers only to a planet or a society.
The word 世界 (Sekai) indeed translates to "world." In truth, it refers to a part of the universe that is pervasive from a human perspective. The simplest example is "the people of this world." For instance, when we say:
この世界には、色々な人がいる。
The literal meaning is: "In this world, there are various kinds of people," but the concept it conveys is "in this society." However, it is also used for broader concepts such as the universe.
But I must ask you: in the Naruto series, do we actually refer to the Earth as "Sekai" in a general sense? Usually, when referring specifically to the planet, the term 地球 (Chikyū) is used. Furthermore, when the story refers to the "society," because the majority are ninjas, they typically use the following terms instead of Sekai:
Ninja World (忍界, Ninkai)
Shinobi World (忍の世界, Shinobi no Sekai)
Sometimes, the term is even used with the suffix for Sage (仙人, Sennin). Recall Toneri in the movie when he spoke to Naruto; Naruto replied, "I will protect the Earth" (referring to the physical planet).
On the other hand, do you truly believe a being like Momoshiki, who is an Otsutsuki—someone who has consumed numerous planets and possesses a "divine perspective" of the cosmos due to his travels—would mean "creating planets" when he says "Gods create worlds"? To suggest that a cosmic being with such an expansive view of space is merely talking about planets is quite far from literary logic and common sense.
Moreover, even if we were to assume your point, what would you do with Hagoromo’s tablet? As I argued in my previous text, we can perceive the entirety of existence through Hagoromo's inscriptions. How can you assign any meaning to the Kanji 森羅万象 (Shinra Banshō) other than the entire universe?
The original meaning of the four-character idiom "Shinra Banshō" (森羅万象)—sometimes pronounced as Shinra Bansō or Shinra Manshō—is "all phenomena in the universe."
森 (Shin): Meaning "dense forest."
羅 (Ra): Meaning "to set out in a row" or "to display." In this compound, it emphasizes the concept of a "vast expanse" or a "wide network."
万 (Ban/Man): Meaning "ten thousand," which in East Asian languages symbolizes "innumerable" or "all."
象 (Shō/Zō): Meaning "phenomenon," "thing," "appearance," or "manifestation."
Altogether, this phrase refers to everything that exists in the world—the entire cosmos and everything within it.
No matter how we look at it, we cannot claim that "God" merely created a planet, especially when concepts like Yin and Yang are mentioned alongside it. There is neither exaggeration nor ambiguity here; it is clear what he did. Therefore, until the story contradicts itself, you cannot dismiss these facts or regard them with unfounded suspicion.