Not having used s3fs I'm going to guess that s3fs is limited due to the limits of the underlying language - Python - namely poor performance overall and poor multi-thread story.

I'd imagine s3fs is useful for stuff like backing up personal projects, quickly sharing files between developers etc.

For operating at any kind of scale - in terms of concurrent requests, number or size of files etc - I'd guess that Mountpoint would be the only viable solution.