As for Brave, I'm not sure that intelligence and good-heartedness characterize how Merida started out--foolishness and stone-cold myopic selfishness seem to better describe her behavior. Of course, I'm not saying that she is really this bad by any means, but she definitely had some learning and growing to do, like many people her age.
There are definitely some "girl power" and male-denigration elements in many movies today that have long since become tiresome, in my opinion, but it's not quite that bad in most Disney movies.
As for the Beast's rehabilitation, Belle certainly was the catalyst, but it was learning to care deeply for somebody besides himself that rehabilitated him, again not unlike Merida, who was the real "beast" in Brave.
Now, the Disney movies that involve "rehabilitating" certain characters are a bit different. These are characters who are still young and need to grow and develop as people. For instance, it wasn't Belle's love that changed the Beast, it was his love for her. She just wanted to get out of that place. Belle did serve as a good example for the Beast as well as the object of his affection, but it was not she who actively tried to change him (the stupid made-for-video sequels notwithstanding)--his change happened on the inside, and resulted in him sacrificing his salvation for her freedom (no strings attached), much like how Belle had sacrificed her freedom for her father's life earlier. Only afterward did Belle realize that she had grown to love him, too.
Cases like this are admittedly rare in the real world among adults (and we are talking about young people in these movies), much like how most criminals are repeat offenders and most serious drug addicts can never fully rehabilitate. Then again, it does happen--some criminals do in fact genuinely reform and some addicts completely overcome their problems. What's really needed is a huge shift in perspective--an epiphany--and this happens on the inside, not just because somebody else did something to you. Watch the Beast when he looked at the enchanted rose after Belle said her father needed her (as well as when Cogsworth questioned him afterward), and for that matter when Wreck-It Ralph looked at the candy hero medal that Vanellope made for him while plunging to his apparent doom--NOW they get it, and finally know who they are. It's a bit more dramatic than most such cases in real life, but that's why these are movies that people pay to watch.