Agreed that it's a higher barrier of entry compared to how simple and slick the c9.io interface was.
I've heard this enough times to know that it's widely agreed upon, but I've never understood it personally.
It's a bit of a nightmare, as a support engineer, to get access requests for AWS services you've never heard of before. "Need access to AWS services: Cloud9, Memento, Athena, and Pandora Nexus." Each having a completely unique set of granular permissions to fumble over means most users get full permissions to the requested service until the auditors complain.
I think the main selling point is that you run the IDE on an EC2 which runs the same OS as your production environment (even Lambda) which allows you to directly compile server code in the IDE and it just works on your server.