5 years at Amazon, almost all as an SDE. I don't really feel like what you've said is entirely accurate.
> for every success Amazon has about a hundred failures
This ratio is off, but even if it weren't it's still not a detracting statement. At Amazon, we're allowed to fail sometimes. Try something quickly, iterate, test, and let it die. Google used to be similar, though they've 'streamlined' a bit more lately.
> outside of the AWS organization you end up working for idiots
Never worked for AWS, can't speak for them. But in my org (Fulfillment) I've worked for incredible managers and a few not-so-great ones but never anyone I'd call an idiot. This isn't a place where smooth-talkin' MBAs thrive. If you bullshit and can't back it up with results, you won't last long.
Most of the MBAs I've met at Amazon were for the Operations world anyways. The Pathways program (https://www.amazon.jobs/en/teams/university-mba-graduate) puts new MBA grads into leadership positions at the fulfillment centers and sees what they're made of. Hard work, but if you do well you go really far very fast.