Games fundamentally require loops because they require skill. You learn through failure and repetition.

Games have the trouble that users have very different appetites for the gameplay. Some want short games, some want 1000s of hours for their $50. Devs do their best to provide a reasonable amount of content. This means that the reality is that most will not 100% complete your game and so you need to tune accordingly.

Its not fundamentally wrong to play a game until you're satisfied. Ideally the game can be structured in a way that the core story thread can be finished by then but sometimes that just doesn't work out.