actually, very few people are saying that systemd should not exist.
What they are upset about is the push to make systemd mandatory (as we saw by the statements about how ubuntu is fragmenting linux by not switching to systemd)
RHEL is the 800 pound gorilla distro, if it does something, it impacts all other distros.
At this point we don't _know_ that RHEL is going to switch to systemd in the next release but the fact that systemd is being pushed by RedHat employees says that it's a real possibility.
I think it's a mistake to do so, RHEL customers have lots of sysadmins with lots of experience with sysV init, and many of those customers have lots of non-linux systems. They also have lots of old RHEL systems (many of them are still running RHEL4 and older)
Making the new RHEL systems have a completely different init system than the rest of the systems they run is not going to lead to happy admins, and taking the attitude that any admins who don't embrace having to re-learn the init system (in addition to all the other things they have to be learning to keep up) are fools who should loose their jobs is not going to improve things.
Many of these admins are working way over 40 hours/week as it is, and have a list of things they want to do (including many that are really rather important) that they don't have time to do that's months, if not years long.
it's not that they aren't willing to learn, it's that they don't see the value of disrupting this particular core piece and having to track multiple ways of doing the same thing, and remember to check which way the box they are logged into at the moment does things.
In many ways, this parallels the Gnome complaints. It really doesn't matter if the new way is better, the fact that it's so different, and therefor disruptive is a large part of the problem