There is however a significant overhead to Docker. Building images takes time (and you will need to build your own, if you rely on any kind of PHP extension such as mbstring, etc) and just wrapping your head around everything is harder than people make it out to be.
That being said, I used to have my own set of bash scripts to setup local virtual hosts, databases, etc, and various strategies to keep configuration contained to single projects, but things always leaked out of the boxes I tried to put it in and in the end all those strategies failed.
So, my current estimate is that Docker doesn't save me much time, but it elevates the quality of the projects I'm working on. So overall I find it worth it to put in the effort to use Docker.