Haven't played IB2, but the first one was very good.
Thing is, it's like an old-style beat-em-up game, along the lines of street fighter or mortal combat. It's just a long series of fights where you punch and kick with cut scenes between.
You have to look a little deeper though, because those old games were also very popular - and for a good reason. It's *not* just continuous slashing - if you're doing that you're doing it wrong and that's why it's boring

It's all about learning the enemy's moves and the best counter to each, and to some extent the best weapons to use too. That's where the gameplay shines, and it's a lot of fun learning how to play it well.
If you want to make it more fun then stop using the shield and block moves except where you absolutely need them. Most enemies in IB1 could be defeated without using either, by learning to parry every move and learning to do the combo moves as your counter instead of just slashing away.