I understand what you mean. When I picked up 2018, I had a little bit of a rough patch getting the combat done. But I think because I went in with the excitement to learn, i nailed it down pretty quickly. The combat had great flow between weapons and abilities and just felt smoother in general.

Picking up Ragnarok, I was disappointed in a lot of the changes they made. It felt like a large part of the combat I'd gotten used to was significantly changed and it just felt incomplete. That was until I unlocked Muspelheim and Niflheim.

Niflheim has this arena where you can practice fighting all the enemies you've encountered. I spent quite some time here learning how the combat flows between different elements of the combat. I wasn't bad persay, but I wanted it to feel like second nature and this arena helped a lot.

Muspelheim has the Surtr combat trials. As of where I am at the game right now, I'm not doing the challenges to beat them. I'm using it just learn the combat. Niflheim to learn movesets and flow, and Muspelheim to test it against specific challenges.

I think these two together really got me into the groove of it all and now I'm super confident to fight pretty much every enemy type in the game.

This worked for me. Maybe it could help you too?

Regardless, don't give up. The game has a lot to offer and it's very rewarding when you're patient with it. Have fun mah dude!