It is not rediculous . GTA games never had masterpiece stories.To say that story and writing didn't play a part in that is also ridiculous; GTA was primarily a single player franchise for most of its life, its setting is basically core to its identity, and it launched the acting career of one of its protagonists. To say nothing of the fact that Rockstar Games has always been on the bleeding edge of storytelling in games in terms of production value. You'd have to ignore so much about the history of GTA and the people who made it to make a claim like that.
In fact the exact opposite appears to be true; open world games with little-to-no story (Saint's Row, Crackdown, Just Cause etc.) have a fraction of the sales of their more story-driven brethren (GTA, The Witcher, Horizon, Spider-Man etc.).
In them the story was always a parody of gangster life in America. That is why you basically feel that everything in them is a joke.
-radio stations don't take themselves seriously at all.("Exploder. Rated PG for having political garbage.")
-You get lots of joke characters per game. You slso have lots of dialogues that are just there to make you laugh.
-You have joke missions.(I mean, flying a plane to release your XXX movie in the city due to this that it was banned ? Using remote control toy cars to explode some gang cars ? )
-The gameplay itself is also parody.(Cars get explode when they get upside down on ground, Ambulances can revive npcs that are dead, Police will free you from jail after killing 1000 cops , police won't follow you when you use paint'n spray etc)
-In GTA 3 a game which made GTA popular the main character was a mute guy that never spoke even once.
Games like Just Cause failed to get GTA level popularity because they never had the variety of GTA.
Saints Row didn't become more popular because the developers never had the budget of GTA to compete with that, but another reason for that was due to how crazier it became compared to GTA.(From what I've heard you get Neo's matrix abilities in SR4 which SR 1 and 2 fans didn't like that direction.)