Your experience is the outlier, not the norm. Most people don't work for AWS.

Sure but I've worked for other places too, not just AWS. Including small startups and mid-sized companies.

All of them had bad juniors--and bad seniors--who people quickly learned could not be trusted with anything and were either fired or put into a situation where they could do minimal damage.

However none of them had blanket expectations of "juniors are too stupid to figure out how to solve problems and need step-by-step instructions." I'm sure some places like that exist, but I'd never want to work there; after all, if the place I'm working for openly admits it hires idiots, what does that say about me?