> I think it should be done by the maintainer of the software not by the distro

Why would you say that? I would agree that the developer likely has better insight into what the software needs. But the security boundary exists at the interface of the application and the system, so I think that both application devs and system devs (i.e. distros) have something to contribute here.

And because systemd allows for composition of these settings, it doesn't have to be a one-or-the other situation--a distro can do some basic locking down (e.g. limiting SUID, DynamicUser, etc.), and then the application dev can do syscall filtering.

In any case, I agree that I'd like to see things get even more locked down. But it's worth remembering that, before systemd, there was basically no easy-to-use least-privilege stuff available beyond Unix users and filesystem permissions. The closest you had (afaik) was apparmor and selinux. In both of those cases, the distro basically had to do all the work to create the security policy.

Also, n.b., that pdns.service I noted is provided by PowerDNS themselves.