I think 4 was trying too hard to come across as "mature" to the point of being flat out cloying, overwrought and stodgy at some points. I mean, a Diane Warren ballad?

A Vanessa Carltonesque, Babyface penned piano ballad? I don't understand how she could mix those songs in along with some of the best she'd ever made -- Love On Top, End of Time and Countdown. That album could have been perfect, but it seems like she was so self aware of approaching 30 and wanted her music to reflect and it stifled her some ways.
The current album is kind of the exact opposite -- there's a natural relaxed maturity there without her taking herself too seriously and being too extra or too preachy or stiff -- it's still fun. She really let go and everything just fell into place so perfectly.