alternate libc's like musl. the eglibc controversy showed this was necessary but poettering initially refused to support a "non-useful libc". his words.
Maybe it isn't as popular as you would have wanted, but I don't think that's the same as claiming it's been hindered by systemd.
Yes and the systemd crowd wants to embrace and extinguish it as well [1]
Being an old fart and sysvinit pundit I am course wrong.