The biggest shift in budgets in the last 30 years has been VFX. It's not like it wasn't a part of action adventure and fantasy films before then. 'Die Hard' was a totally mainstream, non-fantasy thriller and it made extensive use of miniatures for a lot of the big explosions in the film.
But as geek ideas have really gone mainstream we've seen a lot more use of VFX for things that, previously, wouldn't have included them. It's not enough to find a great location, it has to be altered and extended in post. Costumes are streamlined, smoothed out or even completely replaced. Cars can be crashed on set but they're often replaced or added to with CG vehicles. Stunt people can face the cameras because their faces will be replaced with those of the actor they're doubling.
How much of this actually makes better films is a difficult question? How much it makes more successful films is equally hard to answer?
My opinion is that you could pull out between a quarter and a third of the VFX of most blockbusters and the film's emotional effect would be unchanged.
Given my job it would be crazy of me to wish for that, but if studios are ever going to control costs they're going to have to ask their filmmakers some tough questions.