Which they can be dismissed as just illusions since in the original game its never stated that those things where real (unsure about the remake).
And considering that stuff like bullets, regular explosives, or fall from the sky are things that can hurt the cast, or that Sephiroth needed the Meteor to crack the planet, they can be argue to be outliers and that FF7 cast are not capable to destroy cities without particular strong Materia or Techs.
And guidebooks is not different than using lore, as people can argue that they are secondary info that if doesn't match with the original story should be dismissed.
The issue is, actual evidence is needed to make a claim like that. What is the proof that it is an illusion? And it has to be better than incredulity over the exaggerated nature of the attack. A dismissal without proof is not different from trying to hype up a character with flimsy evidence.
The outlier argument is more reasonable (though I already mentioned my stance regarding firearms), especially since the consistency in FFVII is all over the place, and is something I struggle with as well. But even the games themselves keep contradicting themselves. Cloud has to run when he's surrounded by too many infantrymen armed with machine guns, but he's shown to casually dodge lasers. In one scene Cloud is afraid from a high fall, but later he casually jumps dozens of meters into the air like nothing and lands from a fall from hundreds of meters simply by doing a flip in another. In another scene Tifa gets trapped by a locked door, but a while later she kicks a monster with enough force to send it flying tens of meters and crash into a wall. Cloud can't cut down a metal door to pass through, but a while later he slices through several wagons of a train thrown at him. It's a major case of "whatever the plot needs". In Rebirth in particular, the scaling becomes an absolute nightmare.
In the main cast yes, they aren't exactly shown causing mass destruction themselves, but they are shown defeating enemies who can do so, namely the usual Summon fights and Sephiroth (who in Ever Crisis is shown to casually nuke a forest and blow up an entire enemy batallion with a single fire spell). Even if we don't take into account how the story itself explains that Materia requires the users to be strong and have proper affinity to work, that would still be part of their arsenal and be used against other opponents.
The need for Meteor can be argued to be due to the sheer power of the Lifestream, which is constantly shown to be the ultimate power of the setting, even in the ending it's shown that it could even destroy meteor (or push it back so Holy would work if you go by the novels), and certainly doesn't help that Remake retconned the Lifestream into a higher dimension of sorts where entire timelines are born.
My point with the guidebooks wasn't so much that they give their charcters their scaling, as much as they backup and confirm things we actually see on screen. The Ultimania says that it is indeed the Solar System we see during the Supernova and indeed it is destroyed by the blast, the Knights of the Round indeed take place in a different dimension which is actually destroyed by the onslaught, Typhon does indeed turn the Planet upside down, Bahamut Fury indeed destroys the moon and blasts away a continent, and these are all things we see in-game. The whole explanation bit "they use an alternate dimension to unleash their attacks" seem especially made to hand wave why the mass destruction they cause isn't seen outside battle. So they do match and attempt to fit with what the games show. Admittedly, there is some "this dude can destroy the world" but is only shown causing a moderately sized explosion, that being Ifrit, in the low tier.