Besides Who Framed Roger Rabbit, the only other title I know of that used forgotten IPs in a meaningful way and brought awareness back to these older characters was Epic Mickey. No one who wasn't already studying/in the know of animation history knew who Oswald the Lucky Rabbit was, but Disney, in a rare heartwarming move, wanted to bring back their founder's creation from being lost to time. They bought (back) the rights, and then a few years later a video game was built on the concept of forgotten toons jealous of Mickey's fame. It was fucking brilliant, and Oswald gained new life, even if it may have been temporary.
But that was probably helped because Bob Iger hadn't yet grown mad with power, or he never cared about what went on at Disney Interactive.
These corporate suits calling the shots for these cinematic universes just don't get it. All they saw was the success of Marvel and wanted to jump in without a plan, and without studying why it was so successful. Even though bringing back older IPs is a neat Easter egg for animation geeks, they feel so much more gimmicky here than they have ever been in days of old. And to use them as a springboard in a futile attempt to set up a cinematic universe is just sad and disrespectful to Hanna and Barbera's vision. But because they're dead, who cares amirite.