Additionally, orchestrating is simplified with docker-compose vs managing many jails. I used to manage freebsd jails via cli in FreeNAS, but orchestration with docker-compose is much easier and trackable in git. Transferring between machines is as easy as setting up docker, git cloning, and setting secrets. [0] Podman solves some issue docker has, but using stuff like S6 [1] in containers helps a ton. Perhaps most importantly, docker images are reproducible (for the most part) while jails only have templates, so it's up to you to manage reproducibility.
Don't get me wrong- OpenBSD and FreeBSD are amazing distros. OpenBSD has the best user experience in my opinion, which is why I use it for my router. But they suck for modern gaming and stuff like docker.
"custom-compiled nginx version downloaded off some guy's FTP"
This is a strawman argument. But, sometimes one might want custom compilation without installing a host of build tools on the host system. Or one might want to have a reproducible build not tied to the host system. Compilation may be expensive (like with ffmpeg) or the host may be underpowered like a Raspberry Pi. Etc.
[0]: https://github.com/andrewzah/lilac-docker/tree/main/services