An init system isn't a Linuxism obviously. Systemd is though.
Docker is unambiguously a Linuxism. Docker on MacOS and Windows only works by running a lightweight Linux VM under the hood. Docker does not currently run on any of the BSDs, though you can achieve similar process isolation with jails.
Pros: lightweight, really good docs, security as a design goal, designed from the top down as a complete OS so the userland generally all plays nice together and feels more coherent and less bloated than a typical Linux distro
Cons: hardware compatibility/drivers (especially for WiFi and GPU) is worse than Linux, finding help online is worse than Linux, software availability and compatibility tends to be worse than Linux, but generally you can get everything you need especially if you're willing to build from source.
Subjective: Lots of Linuxisms that people are used to having aren't present on BSD. For example, no docker, no systemd, no Snap/AppImage/Flatpak, and no eBPF. This is true even on FreeBSD, which is the most Linux-like of the family. BSDs have their own answers to most of the problems that these tools solve, but you'll have to learn those tools and your Linux knowledge and muscle memory will be mostly useless.