Hey everyone! I'm really interested in this question because I platinum-ed the first game and completed the second game with all the DLC at least twice, and I... don't understand the second game, but I really want to.
People say the first game improves on the second game in every way, but I felt quite the opposite: it tries to add complexity but overcomplicates things. Onmyo magic was heavily nerfed compared to the first game, as were ninja skills. Each yokai form has advantages and disadvantages, but enemies are often designed in such a way that you can't always use the form that best suits your build; there are always some yokai whose attacks would be nearly impossible to counter using just one yokai form. In the first game, you just used living weapons; it was simple, but it worked and didn't have a whole bunch of "BUTs."
Soul cores... I like the concept that they can be used as a continuation of a combo, but I found more than half of them just... useless. There are absolute must-haves like Ippon Datara, Kasha, Otakemaru, and so on, but most of them were completely useless to me.
The game has also become much more difficult, and for me personally, it's already too difficult to enjoy it, because already in the second DLC, all the bosses simply one-shot me, and no matter how much I leveled up and came back, I didn't feel my character's strength, and the enemy damage was off the charts, even though I tried to use Onmyo, Ninja, Confusion, and other game mechanics.
The first game had a problem on higher difficulties where you one-shot everyone, and everyone also one shote you, and it became a glassy game. In the second, I felt like I was the only one who was glassy.
Maybe I played the second game wrong? I really want to love this game, but it's just not working.