I have heard this more and more frequently recently, and particularly from the younger guys/girls - not what they expected, or more often, didn't really know what to expect. One SFO (late '20's) told me that he hated the flying and was bored witless downroute as he'd been everywhere in the first year or so (red-tailed EU W/B Boeing/Bus operator) and wished he'd gone into something more challenging. Heard a story of a cadet who shutdown after the last MCC sortie, tears in her eyes and told the trainer she was so relieved she'd never have to fly as crew again and was just trying to please her parents by achieving something (I understand they'd mortgaged their home and lost their business in the process).
Another option to Denti's suggestion is to try and get into GA flying as you say you enjoyed training - instructing or joining a group flying something a bit more interesting could be an option if you retain any enthusiasm for flying?