Not a big loss, IMO. I still remeber when there was somebody on a dockercon with "I don't accept systemd patches".
I don't see anything philosiphical with that, it's just plain refusal to cooperate in any way with a potential compentitor.
This was several years ago, now this is not an issue anymore, but it's still telling of the toxic corporate culture Docker had back then.
Now that docker has proliferated and the standard practices are clear and well documented, there's less of a danger allowing people to do messy things in their docker containers.
Anyway , the past is the past. Docker were clearly wrong in their decision to put off systemd inside containers, and was most probably for political reasons because it was very very requested feature.