I am trying to form informed opinions on this space, so I'd really appreciate an answer!
Filecoin may not be centralised the same as AWS but they are centralised in other ways.
Any time you have a project like this with $250+ million in VC investment there is going to be an inherent conflict in their goals and motivations versus other contributors to the project.
It's like Spark, MongoDB, Cassandra etc. Yes they are open-source. But the billion dollar companies that are behind them hold all the cards and will win against any attempt to take the project in a direction they don't like.
If somebody else could perhaps speculate about the detailed reasoning behind @sub7's claims (or even their own reasoning as to why FileCoin is a money-grab), that would also be great.
Nowadays there are other companies offering S3-compatible file storage, so at best "S3-compatible" would be federated, but compared to something like IPFS that's much closer to the "centralized" end of the spectrum than to the "decentralized" end.
That is: decentralization is a separate concern from geographic distribution; the former pertains to control/ownership over the data and the hardware storing it, and in S3's case that control/ownership is centralized into a single corporation.