That doesn't mean that there aren't any. Also, FUD (as I understand it) is people spreading unfounded rumours, not people documenting their own experiences and problems with a piece of software. The intent is incomparable.
If you are actually interested in tangible structural flaws in systemd, look no further:
https://suckless.org/sucks/systemd
https://www.theregister.co.uk/2017/07/28/black_hat_pwnie_awa...
Also, see how Poettering handled this zero day (Which grants root to any user with a numeral): https://github.com/systemd/systemd/issues/6237 HINT: He doesn't think it's a bug...
The fact that this even fucking exists in the first damn place: https://latesthackingnews.com/2017/06/29/a-systemd-vulnerabi...
See also: http://without-systemd.org/wiki/index.php/Arguments_against_...