Not everybody can pull off Suiken. You have to be born with it. Its like a natural talent but you have to wield it.

Even though he cant use any of the other jutsus but his commitment to taijutsu is unheard of. Thats why he can open those gates and not many of others can do that. He is not a genius but he is not far away from it.

Also sometimes it takes more than just brains to get ahead. You need determination and courage which he has plenty of.

His life long ambition is to surpass Neji. I hope to see Kishi elaborating a bit more on that in the near future.

I think he has improved in the last three years. I hope one of the Akatsuki member is taijutsu user so Lee can get an opportunity to fight him.

EDIT : Lee vs Neji ?