You clearly see intelligence as malleable, which is great. The problem is many people don't (they view it as fixed), and Dweck's studies show that praising intelligence enforces this view. Dweck talks about good number of consequences of having this belief -- to name a few: encourages associating academic performance with self-worth (aka having contingent self-worth), focusing on grades and living up to expectations instead of learning and growing, avoiding challenging situations, shallow learning, lower achievement, and anxiety/tension and potentially depression.

There's a fine line, and the goal is having teachers that understand how to properly act in order to influence students to take on the proper mindsets (having a belief in malleable intelligence as one).