Most of this is a good thing. Faster. Newer code that is easier to maintain. Less reliance on shell scripts favoring declarative config files instead.
But change has lots of difficulties.
The biggest resistance though is coming from people who are simply accustomed to the old approaches and don't see a problem with them.
But there are other objections from people who think systemd is too big in scope or too controlling or focussed on one technology or another or... some kind of conspiratorial trap or something (http://boycottsystemd.org). I think these arguments are a little hyperbolic since systemd isn't actually a single monolithic system and is really an overarching project to update a lot of major system utilities.
I'm personally more of a Mac user than Linux user. On the Mac, 10 years ago, launchd replaced many of the processes that systemd is now replacing in Linux. Particularly for things like cron and inetd (which were horrible to configure and work with) it was a huge improvement. However, the Mac never replaced as much all at once. It was a much gentler transition. In fact, discoveryd (which does a lot of what systemd's hostname daemon's are trying to do) was only introduced in the current Yosemite.