Titans season 2 seems to have forgotten about the original cast. When Titans began, the show was based around 4 central figures: Robin, Starfire, Raven and Beast Boy, and the entire first season essentially acted as the group's origin story, showing how these seemingly disparate figures came together to become friends and form a superhero group. While the focus was undoubtedly very firmly on Dick Grayson's Robin, every major story ran through at least one of this core quartet, whether that be a romance angle, the looming threat of Trigon or the introduction of the Doom Patrol.
In its second season, Titans has performed somewhat of a soft reset on itself. Many storylines from season 1, such as the existence of the Titans as a superhero team, Dick's beef with Bruce Wayne and Starfire's reason for coming to Earth, have either been altered or abandoned altogether in favor of a fresh approach, a lighter tone and brand new storylines. Although somewhat jarring, this initially seemed to benefit most Titans characters by aligning them closer to their comic iterations but as season 2 has progressed, the original team have faded into the background and the focus has moved squarely onto the older Titans and Jason Todd.
Brenton Thwaites' Dick Grayson remains the undisputed lead of Titans, but his three season 1 companions have slowly vanished into peripheral figures. Starfire's season 2 arc began promisingly, as she encountered an alien ex from her home world who was intent on ensuring she came back and took the throne of Tamaran as the planet's rightful queen. After locking her compatriot away in episode 3, that particular story appears to have been dropped, and Starfire's only real contribution to recent episodes has been reviving Superboy after he got hit by Kryptonite bullets.
Raven and Beast Boy have suffered to an even greater extent. As with Starfire, Gar showed a little improvement in Titans' second season, finding a niche as the glue of the group and getting into a moral conundrum with Jason Todd. Once again, this development took place in episode 3 and hasn't been picked up on since, with his guilt over Jason's near-death experience going unexplored. Gar's absence in Titans is such that his most recent appearance was little more than tumbling out of his room with a "what did I miss?" expression plastered over his face.
Raven, meanwhile, was already suffering after Titans season 2 reverted back to the same 'young girl struggling to control her powers' trope that formed the basis of season 1. She too has performed a disappearing act in recent episodes, and only reemerged to use her powers in aiding Starfire's revival of Superboy. Exactly when Raven began controlling her abilities isn't clear, as last time the audience saw her, she seemed too scared to use them.
If Titans season 1 was Starfire, Raven and Beast Boy's story, season 2 has dedicated the bulk of its screen time to Hawk, Dove, Wonder Girl, Jason Todd, and a handful of new characters connected to the season's arch villain, Deathstroke. The only constant between the two seasons has been Dick. While this isn't necessarily a negative - all of those names are worthy entities in their own right - Titans hasn't managed to find a healthy balance between its old and new superhero teams, much like Grayson himself. The season 2 premiere promised Robin was building "Titans 2.0" with Raven and his other new friends, but very little of this has played out on screen and heroes that were once main characters now feel like recurring cast members with little to contribute in the main story.
Titans continues with "Atonement" November 1st on DC Universe.