So given a manager/employee could do effectively what a MBA can do, why would a company hire a MBA degree instead?
However I started my career as developer and have spent 7+ years in developing complex systems. The one difference I could always notice was leadership/initiative distinction between me and other developers and I used to think why these guys are not able to manage their time and guide their juniors. Simply they were not able to think beyond code(I am not generalising but the pattern I noticed with obvious exceptions).
I'm not saying your MBA hasn't helped you. I'm just saying it's not a magic bullet (unless a company requires an MBA to get in the door). For most situations, just having a basic understanding of accounting & finance is enough, and for the times it isn't, knowing how to organize and lead a large multidisciplinary project is. That part's tougher and all the theoretical knowledge & case study readings in the world will only get you so far.
There are well-defined scenarios where an MBA has some value. Agree with you that managing developers is typically not one of these scenarios, but I don't believe b-schools typically frame MBA programs as a means to teach management of people but rather management of well-known business problems.
A good proportion of managers get promoted due to necessity rather than merit (as mentioned a the beginning of the OP). This issue is more conspicuous now that employees of fast-growing companies are more open about this issue and have time to blog about it (as growth has become somewhat more efficient).
Would love to see the space of engineering management get "disrupted" by high-quality, community-reviewed, and freely available publications. Might not 'kill MBAs' but will help people decide if they even need an MBA.
As can engineers. Aside from the presumption that MBAs want to and are hired to do this kind of stuff, and will put in 100% of their time doing it, there's no exceptional value that the MBA education in itself brings, IMHO. Most of this is stuff that a reasonably smart person would be expected to pick up on the job. The MBA does not learn enough finance/accountancy to do a CFO/accountant's job, nor does he learn enough to do a lawyer's job...