That's complete bullshit.

Mako was THE hero of the finale. He battled biplanes hand-to-hand for God's sake!

Bolin was played as a doofus from the start, and we never saw him succeed with any woman, ever. And the stupid moustache picture is from the 3rd episode.

Korra turned unsure and "weak" the moment Amon entered the story (also ep.3), and she broke down sobbing at the end of episode 4! Of course she is portraied "strong" at first, she grew up completely sheltered! During the first season she develops from the adversity and comes out stronger. And yes, Aang even confirms that she "hit her lowest point" in the finale, but on the whole she gets a lot stronger, smarter and more controlled. Her story arc isn't the opposite from Aang's in ATLA, it mirrors it completely.

And Asami was always a secondary character with important roles to play during the middle and end of the story. In fact she was INTRODUCED as a boring love interest, to enable wacky love triangles, and only got interesting a lot later when we got to know her father a bit more.