Guys, I know what happened is weird. However, I think that just like every other action in the manga, Kishi did not make a plot hole if we consider real interpretation. So, take it this way:
0. The initial context: Humans are used to normal gravity. They don't get pinned down in general
1. Change of context: Suddenly, everyone is taken in another dimension where they feel heavy
2. Primary reaction: Obviously, at the face of the unknown, they have to feel it, and realize it. Does it mean they can never overcome it? My answer is no.
3. Instinctive action: In Naruto, every character has his own mind. The action is quick, and people like Kakashi and Obito have lived long enough to not take a chance. They are shinobi, and they have to act as fast as they can. They take their all and rise for their student and friends. Does it means that Sasuke and Naruto cannot do the same? My answer is no.
So, the point is that Kishi is not asking each character to do something as we try to think. Rather, Kishi is telling a story that comes by inspiration. He creates character with their own strength, flaws, and logic. Characters are not linked mentally and have individual thinking and reasoning. In fact, kakashi was already depressed before the action, and was trying to figure out what he can do with is seemingly useless self. Obito had already had his resolve to die with a last good sacrifice.
So yes. If all our so self-proclaimed smart, creative, and intelligent brains are really working properly, we can realize that the action happened in less than a second (total time). We should realize that each character in the manga does not give a **ck about what we see and what we know about the character around them and the big picture we have.
My point: There is actually no plot hole or stupidity. Rather, there was an awesome sequence of action - that is Kaguya fired quickly two sequence of bone. While naruto and Sasuke was dodging the first, she fired the second before the two were even ready to respond, forcing Kakashi and Obito to take their last effort into action. If you are butthurt, who cares?