Once considered one of DC's most popular superheroes, Green Lantern is now a B or C-list character with little hope of advancing in ranks - and though DC has the tools to fix the character, they steadfastly refuse. Armed with a ring that is only limited through the user's imagination and willpower, Green Lantern has the potential to be one of the most versatile and interesting characters the company has ever fielded. Unfortunately, the past decade has seen a noticeable decline in Green Lantern popularity, and this can be attributed to one element above all others: Hal Jordan.
Green Lantern, while not the first legacy hero, is still one of the most well-known. Alan Scott, the first Green Lantern, debuted during the Golden Age of Comics in 1941; his ring was magic-based and infamously couldn't affect any object made out of wood. The character was changed radically in the 50s to test pilot Hal Jordan, who obtained his ring from a dying alien. The revamp introduced an entire legion of Green Lanterns, each acting as galactic police officers who kept the peace between worlds and apprehend criminals. As more Green Lanterns were introduced, such as John Stewart and Kyle Rayner, DC continued to use Hal Jordan as the prime Green Lantern...a mistake they soon came to regret.
Perhaps in part due to his straight-and-narrow heroic characterization during the 50s, Hal Jordan began to garner a reputation as a weak character. His personality was not particularly interesting, especially with Stewart and Rayner in the books (and Stewart was even used in the Justice League animated series specifically because the creators found him more interesting). 2011's infamous Green Lantern film starring Ryan Reynolds was a box office disappointment, but DC continued to push Jordan as Green Lantern nevertheless, using him in the New 52 (and even keeping his entire backstory while other characters like Superman had their entire histories erased).
That's not to say that Hal Jordan doesn't have the potential to be a good character - Geoff Johns and others created excellent stories in the form of the War of Light and Blackest Night series. Unfortunately, Green Lantern is also a victim of his own power - the Power Ring is one of the strongest weapons in the DC Universe, and Lanterns with even a modicum of creativity can solve most problems in minutes. Proper Green Lantern villains are difficult to write; in a way, Green Lantern has his own "Superman Problem" in that he's far too powerful for regular foes.
DC's problems with Green Lantern are threefold: they are reluctant to use anyone other than Hal Jordan for their "main" Green Lantern, the hero has powerful abilities and must have powerful foes to match, and public perception is at an all-time low following a failed movie and a decade of absence from the DCEU. These are not insurmountable issues, but perhaps the changes DC needs to make are too radical, at least for now. Green Lantern has plenty of fans, but he isn't getting any new ones lately, and DC has the ability and skills necessary to change the legacy character's fortunes around. They only need the willpower to act.