you're conflating the success of the technology with the success of its users. If the measure of success for a technology is that a lot of people are using it

you're conflating the success of the technology with the success of its users. If the measure of success for a technology is that a lot of people are using it and working on it, then Docker is tremendously successful. If the measure of success is that the company building it is profitable, I have no idea. If the measure of success is that the founders can raise a lot of money and then take some off the table ... gonna bet successful here; they've raised $248m. Whether or not it's a good way to run applications is entirely irrelevant based on those definitions of success for the technology.