The JL is all of DC's biggest names gathered in one team to handle the largest threats (not just cosmic either), while the GL corps is basically a police procedural in space. The Teen Titans is the next generation of sidekicks teaming up together, the Suicide Squad is supervillains being forced to do the government's dirty work, and then you have the Doom Patrol being the freaks dealing with situations too bizarre for the rest of the DCU.
All those teams have an easily understandable hook that the Titans don't have. The adult Titans is a group of 20-somethings (most of whom are just younger copies of the JL members) hanging out and fighting boring villains. Manhattan is nowhere near as interesting or colorful as Gotham City. They're in a weird spot that they've been stuck in since Wolfman ran out of gas, and there really is no way to get them out of it until the JL is permanently retired and they take their places, and there is no chance in Hell of that ever happening.