Kingdom Hearts is only hard if you're one of those people who mindlessly attacks enemies without checking your surroundings.
Play defensively and only attack when you see an opening that won't get you kill. Every single enemy telegraphs their attacks so it's easy to know when and how to dodge them.
Yup. People joke with the Dark Souls comparisons, but if you approach both games similarly you won't have much trouble. Don't get crazy attacking and think before selecting commands, dodge when necessary, and you'll do great.
You're calling the combat mashy and mindless though so it's no wonder you're having a bad time.
I honestly don't remember having much trouble playing this as a teenager outside of the endgame and obviously challenging stuff like Sephiroth and company... Oh, and some of the platforming, but I imagine that's improved in the PS4 version due to it running at 60fps.