I just don't think she's picked the 'meatiest' roles that she could have done since LiT. It's been general popcorn fare, which has naturally ended up dropping her back in with the other popcorn actresses.
But....that's where the bigger paycheques are. Perhaps she's not even that worried about whether people have a high opinion of her acting. Maybe she just likes the job and does what well-paid stuff comes along. No doubt she could have chosen a serious drama over Avengers if she'd really wanted to challenge herself...
Although, she's already won her Oscar. So she doesn't exactly need to sign up to one of those intense, full-on roles to get attention (eg Berry with Monsters Ball) at any point in the future. She's dodged a bullet in that regard, by winning her Oscar so young and for such a low-key (but decent) performance.