Hot take: Junkrat is a powerful hero held back by the fact that no one likes hitting directs and all the olden Demoman mains who actually do like hitting directs are confounded by how strangely floaty his grenades are. Same reason people thought the Loch n Load from TF2 was awful - no rollers for those who didn't like directs and a different grenade arc for those that did, and thus had a lot of muscle memory.
Also, yeah, Zarya doesn't help either.
Also, yeah, Zarya doesn't help either.