Systemd and Linux Network Namespaces together are terrible, although each is very nice individually. I have seperated clearnet access and dn42 access via netns in a lab setup. For each program I wanted to use in both namespaces, I had to copy-paste and customize the Systemd unit. This is terrible. Too bad Systemd doesn't support this natively, but only with tricks.
What kind of reason is "I don't like the concept"?
https://github.com/systemd/systemd/issues/2741
Personally, I find netns very handy because you can easily isolate networks (for example, dn42 and the Clearnet). This is also what Kioubit does in dn42, for example. To reject a proposal with this reasoning I think is wrong.