Like all humans, tabletop gamers sometimes make irrational choices. We do it in our games, but we also do it when choosing what game to play. I've written before about how I sometimes play a video game for its soundtrack, and I'm happy to admit that I play some tabletop games for seemingly trivial reasons. Choosing to play a tabletop RPG or wargame just because you like the look of the book is literally judging a book by its cover, and seems like a recipe for disaster, but somehow, it does work. I'm not here to recommend it, I'm only here to defend it.
In the realm of immersive games, one of the roles of game rules is to provide structure for your desire to be immersed in the game world. Of course game rules have another important function, and that's to create a game that can be played. But each player gets to balance the importance of those two roles. You might decide that the game mechanics are really important to you, because after all that's the reason the thing's a game and not just an art book. But you're free to decide instead that all you really want is an excuse to participate in a series of thought exercises in a fictional setting that you enjoy. Sometimes, that's the value of a book or board game or card game (or whatever) that's particularly bad at being a game but that's really good at, well, looking good.
Once you've been a gamer long enough, you know the games I mean. You might have your own examples, but for me Shadowrun comes to mind. There are easier ways to play a cyberpunk RPG than to resort to Shadowrun, and yet I keep going back to Shadowrun because I enjoy Shadowrun. I'm not looking for a cyberpunk science fantasy RPG that looks and feels like the Sixth World, I'm looking for exactly what I get from a Shadowrun book. I want the weird layout, the in-universe narration, the fictional usenet posts formatted as a bullet list because the layout artist didn't know any other way to highlight a text admonishment, the over-complex weapon rules, the over-complex magic rules, the over-complex everything. I want to be abused by Shadowrun because, for whatever reason, that's become part of my Sixth World experience. (Not enough to switch to 6th Edition. We all have our limits)
It probably seems like I'm just saying that sometimes style overtakes content, and some people are happy to relax with a stylistic book and call it a game. There's more to it than that, though. Planescape back in the 90s was just as playable as D&D itself, and yet the main appeal of it for me and my friends was the conceit of the setting. Admittedly, the art did a lot of heavy lifting to express that setting, and that was definitely influential, but I don't think there's a reasonable argument that Planescape wasn't a well-designed game. It was AD&D and was, at least insofar as AD&D was, beyond reproach.
But Planescape had such a powerful identity that it transcended the D&D brand for me and my friends. We knew it was D&D, but we also sort of forgot it was D&D. It was Planescape first, and it got mixed up in a meta-fantasy world of Dark Crystal and Elfquest and Labyrinth and Mirrormask. We didn't create characters to play Planescape. Playing Planescape for us was more about flipping through the books and following through on conversations inspired by the different philosophies of Sigil and the planes.
What's the inverse of playing a game only because you enjoy the idea of the game? Well, interestingly I don't think an inverse exists. The inverse is null.
When you don't have a rulebook or sourcebook for a game world, then you have no excuse to sit around your house doing absolutely nothing but pondering that game world. Or at least, that's how it is for me. Were I to set aside an hour to ponder the Sixth World or Sigil or the Fallout wasteland or Bureau 13, my mind would wander off into any number of tangents, or else I'd realise I was wasting my time and I'd go do something "productive".
A game, whether the mechanics are good enough to play or not, can serve as a focal point for feeling like you're playing the game you want to pretend like you're playing. There are several levels of abstraction available.
And so on.
Sometimes the presentation of a game just happens to appeal to you, and so you decide it's an enjoyable game. It may or may not be a game you recommend, but you enjoy the conceit of the game. Is it really a game if you don't play it as intended, or when you play you have to ignore half the rules because they're broken, or if you just don't play it at all?
Yes, it is.