As others have pointed out, the evolution of teenage culture (and culture in general) has shifted drastically over past years. Teenagers today, they can get whatever exploitative, sexual, or violent curiosity satisfied online. When you can google your most bizarre desires and have 100k results returned to you, the sexually violent video game world seems meager. It's allowed, it's been approved, it's been created with hard work and dedication of teams of programmers and designers and executives. You can't compete with a raw iphone cam of the same stuff happening in real life.

Another change is the loss of shock value and creative freedom in general. I immediately thought about the similar transformation of South Park.

South Park used to push the boundaries to be shocking; seeing what they could get away with in every episode. Now they can pretty much do anything and the show is much less entertaining and interesting because of that.

There is a documentary on Netflix called The Making of South Park: 6 Days to Air that touches on this. While the documentary is mostly focused on the creation of the episode and the process, it reveals how much has changed in terms of what they can and can't get away with. Because people have come to expect being shocked by South Park now, they don't care to spend the time and energy getting upset anymore. Another part of this is our society is generally more liberal and accepting of gross or overtly shocking imagery. But it isn't that we are "accepting" in the sense that we suddenly believe it is okay. Rather, we see it as what it is: a gimmick in order to elicit a response. Similar to our response to trolls online, we no longer feed the egos or sadistic nature of the creators. We realize that they get off on eliciting a response and it is better to let them be. They are nothing if we are not shocked.

In South Park's case, this new lack of limitations has given the creators far more freedom during the creative process. This freedom has led to the faltering and steady demise of the show's quality, or rather, the shows reputation. The show was never quality entertainment but it did exactly what it intended to do: push boundaries, push the limitations of the executives and lawyers and shock.

There is another documentary called The Five Obstructions in which Lars von Trier challenges his mentor, Jørgen Leth, to make his film again but with limitations. The obstacles he places on his mentor force him to be highly creative. With unlimited freedom, you have too much room to think and the heart of your idea is never fully developed. If you can go in 100 different directions, you will, but you will never follow the 100 paths to a satisfying completion. With limitations, it forces you to focus on one sole objective and achieve that goal and make sure your ideas are perfectly aligned to meet that goal.

I think all of these things contribute to the place GTA V is at today. They have no limitations. The shock value is gone. The technical abilities of what a video game can be is gone. And their original audience has grown up and now sees through the gimmick. The new audience of younger teenagers doesn't GTA V in the same way younger teenagers did 10 years ago.