Scrum has the particularly noxious side effect of driving underground any sort of drive to improve and to learn new things. An engineer in a Scrum team is an engineer, has his or her lane, and is largely expected to stay in it. Learning? Branching out? No, get your promised tickets done this week. That concerns me; while it's possible for a Scrum-based shop to invest in its people, it's not part of Scrum to really do so. And the people are what matter, at the end of the day, so I find it rather dehumanizing.
(This is a big part of why I'm moving towards consulting--so I can invest in me more often.)