I think it's more that the megacorp business model is fundamentally incompatible with making good video games. Their only reliable competitive advantage is money, they can spend more on a single project. But if they spend so much, they can't go as risky as indies go. A ton of indies publish shit games, it's just that some are absolute gems.
Point is, AAA games can only match indies in originality if they are okay with tanking the IP and the studio just to make something original. But since they are megacorps, they will never be okay with that. The also can't amortise the risk over a lot of small projects, because then they lose the ability to outspend indies and would have to compete with them directly.
It's like a sort of inverse economies of scale.