The reason I prefer google drive / iCloud is (I think) they have backups so if a truck or a comet hits one of their data centers, my files probably won't be lost.
Whereas I don't think that's true of S3. Perhaps someone can correct me if I'm wrong, but I think with AWS/GCP it's up to the user to manage redundancy.
My view is that Google Drive and iCloud will cost significantly more, but that is getting you a nice web interface where you can see your files. And maybe other features like sync’ing. Also, customer support.
I like AWS S3 because I trust my data is more secure there and it is much cheaper. I also trust the durability of s3, not sure that Google Drive or iCloud discloses so openly how they replicate data or if they have an SLA like S3. But S3 takes some technical knowledge to understand how to manage things in a cost effective way. And you won’t get help from AWS support unless you pay for a support plan.
Also the person you are responding to is obviously wrong. S3 is the most durable of all. iCloud and Dropbox were using S3 at some point.