Big wages and respectable roles don't always go hand in hand. If you want the big wage, that often requires doing a lame film but one the mainstream youngsters enjoy. Doing a respectable role might require accepting a relatively much lower wage. This is the obvious reality. Accept it or not, its their choice. Don't complain, though.
Film studios are primarily a business, so I don't blame them for churning out films I dislike. They cater to different tastes, and to the highest demand.
The blame lies with those who pay and subsequently create a demand for films like Transformers. Having said that, I'm overjoyed that John Carter flopped, and probably prevented its franchise.