We use docker-in-docker as well to deploy our Jenkins workers. It has it's pros (running Ubuntu 18.04 and Ubuntu 20.04 workers side-by-side and ease of pushing out an update) but it's fragile and confusing. Things can get really hacky when you need to start sharing volumes or injecting additional configuration.

I'm much more confident with packer now though. Next time I do any major work on our Jenkins infrastructure I'm ripping out docker-in-docker for the workers and replacing it with packer built images.