Full disclosure: I work for Linode and I am super biased. This is my own opinion etc etc Perhaps the first AWS mistake you might make is... using AWS? Even before I started at Linode, I thought it was terrible. It's extremely, unreasonably pricey. The UI is terrible. Their offerings are availble elsewhere. I started MediaCrush, a now-defunct media hosting website, on AWS. After a while, we switched to dedicated hosti…
https://aws.amazon.com/solutions/case-studies/
I see your characterization of AWS above as "terrible", but I'm curious how that squares with the (probably very well-informed) decisions these people made to use AWS.