They killed their Docker offering right about after they launched it, mostly because it's too difficult/expensive to scale containers, so they forced their entire user base onto the serverless paradigm, because it was convenient for them. Their PR story is it's "better for everyone", except there remain use cases (aka websocket support) that remain unsolved for months on their new platform. To give them credit, they didn't fully deprecate Docker-- old customers can use it, for an indeterminate amount of time.