Everything in that fight was just bad.
It's absolutely not understandable why they didn't go with the original, which could've looked bad also, but at least it wouldn't have been as bad.
The whole scene in which he flew away with the monster for a few miles just to land directly in front of the cage again was absolute garbage too.
Way to ruin an awesome monster... when it lost both it's eyes during the manga fight, and tried to go out in a final blaze, overpowering MC like that, it was really cool looking.
Same issue with the girl climbing up the hill/cliff, just so it could drop down from it (which took so freaking long too, lol). Such a weird way for ther to join the fight again.
And worst of all, this clearly looked like the girl did all the work, he did basically nothing. That's just not what was supposed to happen and makes the girl hyping him up annoying.