My experience as a Development Manager for the past ~year (YMMV):
1. I'm playing chess; senior management is playing checkers. No, not because I'm some sort of genius and they are simpletons, but rather they talk about interchangeable "resource units" and I know these FTE's as "Tom" and "Amy", each with specific strenghts and weaker areas. Big strategic plans cannot differentiate but we front-line managers need to figure out how to position and leverage individuals.
2. Actually, genuinely, caring about your direct reports goes a very long way towards solving a lot of culture problems but...
3. Dev Managers need to put a lot of effort out into their teams to drive change and it is often (most of the time?) not returned. Your biggest enemy is not active sabotage, it's apathy at all levels of the organization. I started pushing for some specific cultural-ish changes about this time last year and, while I was given passive approval & support and lots of latitude to make change, it has been physically exhausting. If I was in an organization that didn't even give me this much freedom it would have been exhausting and pointless.
4. A Dev Manager can make localized changes when not all teams want or can reciprocate, but I'm not convinced yet that the requisite firewalls you need to erect aren't ultimately harmful in the long run. It is a very delicate balance.
In the end my take-away is you need space and time to make any meaningful change, and even that is limited by the crushing inertia of the organization. For me personally it has been physically consuming and I have 6 month & 1 year goals, plus an overall 3-year plan that I'll either complete in the coming year or look for an new opportunity elsewhere.