I think that systemd oomd is pretty slow. I get a quite a few minutes of unresponsive system while waiting for oomd to do something. Honestly rebooting is faster than waiting for it to work.
I recently installed and enabled earlyoomd on fedora, and on an initial test, I still got an unresponsive system with the default settings, but after around 20 seconds or so, it killed the responsible process and I was able to continue working. Not perfect, but much better.