Because it requires a pickaxe and it falls to the ground. Those are the reasons it was worth having. You could break it with your hands and instead if dropping, it went right into your inventory. I see almost no reason to use these ever, and they used to be one of my favorite things.
I'm sorry, but extra utilities 2 is a downgrade from the original. For the most part, I'm loving the 1.10 stuff, but this one has been disappointing.
Okay, so - once one is aware of the block's behavior, it's a simple matter to compensate. Since you're using an Angel Block, you probably have the ability to fly (otherwise, you'd be pillaring or scaffolding out to 'where-ever'). Place the block one level higher than your intended structure, and place the first structural block directly underneath it. Even if you're using it to start a water build, you've got this ability, although having a few (2-5) disposable blocks in your inventory might be necessary to get up on top of the block. Stand on the Angel Block and break it with a pick, and it'll pop into your inventory.