I would guess the network egress costs, specifically, might justify a blanket statement like...
"If you have content where you can't put a cache in front of it, and it drives significant bandwidth use, then AWS is not a great option"
"If you have content where you can't put a cache in front of it, and it drives significant bandwidth use, then AWS is not a great option"
Data driven applications on AWS are already expensive because of the high traffic costs, but storing/serving media on S3 single handedly lets your bill explode. For everyone who feels like the statements above are exaggerations, just check out their actual prices (https://aws.amazon.com/ec2/pricing/on-demand/) in comparison with a regular CDN (https://www.stackpath.com/pricing/).