I think playing a single game(especially an online one) constantly can become an issue. It can get a bit OCD with win/loss ratios and trying to get better every run with frustrating returns. This can spiral out of control and cause an unenjoyable time sink.

Although, there are a lot of games out there and I think its good to not write off the medium entirely and to broaden horizons as far as what you play. There's lots of great experiences out there that dont require playing 12 hours a day, every day. As people have said, moderation is key.