Well, in part 1 the final fantasy crew jump to endgame final fantasy levels and fight a god, an alien, and obsessive girlfriend sephiroth.
So, they leave to go find sephiroth but there is basically no threat out there besides him that can fuck with them now unless they add more convoluted shit to ff7. Like weapons suddenly appearing in the next town after midgar or some shit.
But it messes with some scenes where they were impressed with strength adding this kingdom hearts crap.
My understanding of that fight scene is that they're fighting in a singularity where time and space are doing weird shit, and that they won't be able to do this stuff anymore once they're back in the real world. I'm also totally expecting Yuffie to show up and steal all their equipment near the start of the next game, so kiss all your leveled-up weapons and materia goodbye!
Remember the snake and how impressive it was as a show of sephiroth's strength to the party? Not so impressive when they killed a fucking god and beat back Sephiroth.
I wouldn't have cited the Midgar Zolom actually, I would have cited the flashback to Nibelheim segment in Calm when you fight next to Sephiroth and he does 1000x as much damage as you do in the battle system. But maybe that's because I always went to the chocobo farm first and never tried to fight the zolom so I never got that perspective of Sephiroth curbstomping this unbeatable monster.
The problem with just doing the same thing again is that FF7 Sephiroth had the benefit of being a completely unknown figure aside from what the writers decided to drip-feed you throughout the story. But FF7R Sephiroth has had 20+ years of being one of Square's most famous villains, the Zolom scene just isn't going to impress like it did before when everyone knows that endgame Sephiroth throws planets at you and stuff like that. It's like expecting everyone to be shocked and sad when Aerith dies again in exactly the way that everyone knows she's going to die, you're just not going to get the same emotional impact out of scenes that everyone sees coming from a mile away. Sephiroth isn't really mysterious to anyone who's played the original game, but when you do a second playthrough and you start seeing shit like how Sephiroth is apparently from the future and all that stuff he starts being mysterious again because now you're wondering what his new angle is and how he's going to do things differently.
Also, "beat back" isn't the way I'd describe what the party did to Sephiroth. He just kinda left after no-selling Cloud's attempt at Omnislashing him in the final scene. And this is just one of his inferior clone bodies, the real thing is still chilling out up at the Northern Crater.