On the other side, a really good developer has the knowledge and experience to frame the problem in an understandable business context when communicating the issue and options to management. Some of the best work experiences I've ever had were in orgs with such experienced developers and managers. Working together we were often able to solve apparently intractable problems with creative options which would never have been conceived absent the clarity of thought and communication on both sides.
I feel like the "20% time" paradigm where one day out of the week is left up to the developer to schedule (within reason) is the right way to balance the conflicts of interest and still leave room for people to be curious.
Maybe a long load time just wasn't that important for the success of GTA.
I guess it's possible that the engineers who were talented enough to create this extremely impressive game in the first place somehow threw up their hands and said "guess it can never take less than 7 minutes to load, best we can do". But it seems much more likely that they were well aware, but never allowed by poor management to go back and fix it. The game was released and printing money, why bother. They're on to the next title.