>>hkmura+(OP)
I do consider myself a specialist in cloud computing (of which storage is just a component). I think it's important to become really deep in one or two areas, even if you are a generalist. For example, cloud computing has too many services to be an expert in all of them, but I do consider myself very deep in data and analytics (Hadoop, Spark, data lake concepts, etc.) and containers (orchestration, service discovery, CI/CD and deployment automation).