Its funny that this specific mission gets mentioned, because I watched my 12-year old brother play through this thinking the exact same thing on Christmas Day. I frowned, since the game was trying to teach him with tiny text tutorial blurbs off in the corner of the screen while he was driving at 80mph. But then I looked at him, and he was having the time of his life, despite his repeated failures.
That mission in particular is a pretty significant set piece, and the mass appeal market ('casual' can be a loaded term) want spectacle, at least when it comes to single player. He didn't really care about hitting the fail state, it was all new and exciting for him. He eventually got it and went on with the game, got bored, and started multiplayer.
Now, I'm not saying that GTA hasn't committed these game design sins. They totally have. But in the grand scheme of things, I feel it doesn't actually matter. Hell, a start-stop-start-stop tutorial can even be as frustrating as an unwarranted fail state to these people, especially in the 'point gun, shoot thing' common ground that most AAA games share. They just want to dive in and be entertained at the end of the day. Shooting a guy off a stolen yacht while in a sportscar while weaving through traffic at 80mph while making witty banter is, as a matter of fact, entertaining at the end of the day, whether or not you fail at it a couple times.