I think this is valid, but there is also another option. In my 4th year engineering (my Masters) I took 3/8 of my courses outside the engineering school: Accounting & Finance; Operations Research, Entrepreneurship. I am extremely glad I took Accounting & Finance and Operations Research - I would highly recommend Accounting and Finance to any undergraduate who thinks they may work in management at some point in their career. The Entrepreneurship was very dry, and I can't remember a single thing that I learned there.
The two scenarios I see as valid for doing an MBA:
1. A lifestyle choice (albeit a very expensive one)
2. To get an opening into consulting / banking if you don't already have a background in it (though there are other ways to do this too). Having worked with many MBA hires in consulting I would say the value of the MBA is putting oneself in the pond from which consulting companies fish, and much less so teaching the skills that consultants need.
If I was to go back to academia, it would be for a PhD for sure.
On your description of courses, well OR was what I did my ABD in, so I'm biased. I personally loved my Entrepreneurship course. I think its professor - dependent. Our professor was a bit of an entrepreneur (and entertainer) himself.
Totally agree. Ours was not an active entrepreneur, though he was a friend. Additionally, I was involved in running the university entrepreneurship society, through which I was exposed to many excellent talks by entertaining entrepreneurs - those made much more of an impression on me.
Unfortunately the programs seem to be full of business undergrads, who go straight from their undergrad and (I guess) see it as a way to differentiate themselves. If your undergrad is not in business, then the accounting and finance training alone is worth it. And lots of people do the degree part-time (as I did) so the argument that its a waste of time doesn't hold up. For the right type of person.