The viewpoint is interesting, but I pretty much don't agree with it at all. Having just completed the game moments ago, I can certainly agree that all three protagonists are horrible, horrible people, and they were never supposed to be anything else. That doesn't indicate poor writing, it simply indicates that this is a story about three horrible people, and it happens to be a very interesting and enjoyable story in my opinion.
If you can't separate your own sense of morality from that of characters in games or other media, that's fine, and I'm sure it would make playing this game (or many other games for that matter) extremely hard, but I don't think that applies to most people at all.
Also, the context for that assassination mission was that Michael was doing a favor for Lester in order to gain his help, Lester's motivation was left vague but considering all of his other assassination missions it was almost certainly to game the stock market in some way. I honestly don't get what is different about the context to this mission compared to all the other missions in the GTA series.
If you can't separate your own sense of morality from that of characters in games or other media, that's fine, and I'm sure it would make playing this game (or many other games for that matter) extremely hard, but I don't think that applies to most people at all.
Also, the context for that assassination mission was that Michael was doing a favor for Lester in order to gain his help, Lester's motivation was left vague but considering all of his other assassination missions it was almost certainly to game the stock market in some way. I honestly don't get what is different about the context to this mission compared to all the other missions in the GTA series.