Most of us are perfectly capable of learning new technologies, and there is no shortage of software and disciplines begging for our attention and adoption. For me it's not a matter of "can I learn this" but "do I want to spend my most limited resource--time-- pouring through docs and tutorials to become a few levels below competent at x, y, z, etc, etc, etc interesting systems." Some systems are intrinsically rewarding because they yield thinking tools that can be applied to other systems, while others, like Docker, are pretty much never fun and just a tool.