Aquaman has a bad rep for one reason: Superfriends didn't know what to do with him. And to be fair to the show, he doesn't fit as a regular member of a team that operates primarily on land divided into nations.
1. Aquaman is the ultimate anarchist superhero. His father (or, in some versions of his origin, step-father) was an American and his mother was an illegal alien, an Atlantean. He grew up an outcast, a citizen of no nation.
2. Aquaman works for justice on the whole planet, but especially on the three-fourths where human law is weak. Every other superhero has a home beat, the city they live in. Even Superman, who should be international, is seen by the world as an American because he operates out of Metropolis. Only Aquaman roams the world.
3. Aquaman is strong enough to survive at the bottom of the sea. How many other heroes can keep him company there? Only Kryptonians, the Marvel Family, Green Lantern, and a few magical folks.
4. The creatures of the sea obey Aquaman because he's just that awesome.
5. Aquaman has a strong enough sense of self-worth to marry someone who is objectively more powerful than he is.
So, what mistakes have been made with Aquaman?
1. Originally, he didn't have any limit on how long he could be out of water. A limit makes sense for Atlanteans, but Aquaman should be unique, half-human and half-Atlantean, incorporating both group's strengths and neither's weaknesses.
2. He should never have become King of Atlantis. The job should've been offered and rejected.
How would I write Aquaman?
He and Mera are kids in their early '20s, cruising the world and looking for adventure. She has the power to shape solid things out of water and he does not, but she can't stay out of the water for more than an hour or two, while he can survive anywhere a human or an Atlantean could.