The game you play for a thousand hours, but that doesn't mean you enjoy the game. We've all seen the image of someone writing a negative Steam review, with more than five hundred hours of play time. Let's face it, that's just not an absurd idea anymore.
I've invested hundreds of hours in Fallout 4, and I may have enjoyed about five. The rest was just the promise of entertainment, with the bloody 'kill loot, kill, return' gameplay loop fooling my brain into believing it was having fun. Then I've heard what you've said about Skyrim and you've returned to it again. The whole of us.
But Old School RuneScape? I'm not sure. It's usually easy to spot one of these games that consume your time, and then you moan about it online. However, RuneScape is completely different. Even when I'm not playing I don't have an opinion about it. I can listen to the music in my head and feel a attraction to the music. It was discovered that it was in my phone was a blunder. My family hasn't spoken to me in weeks.
RuneScape was among the trailblazers: a game purely focussed on engagement, which doesn't necessarily have to be in tandem with having fun. However, that doesn't mean that they're incompatible It's just you can find ways to play even when you're not having enjoyment.