Earlier quoted context omitted.
Even Linux kernel has had tons and tons of vulnerabilities and bugs. Not to mention non-systemd core system components and services have been found exploitable times and times again. You can't set higher standards for systemd than other core pieces of software, it's simply not fair.
The Linux kernel has high standards. Most of the bugs come from the drivers. If systemd wants to be the end all be all init replacement it should have known from the start that it needed to meet a high bar of code quality.
If you want to systemd to adhere to really high standards then you're a hypocrite if you don't apply the same standards to every subcomponent of a non-systemd system, be it upstart, logrotated, cron, chrony or whatever else.
But it seems to me that you actually don't apply the same standards to the alternatives, they've all been hit with some vunerabilities, they all have bugs, they all have at least some terrible code, some lack maintenance or are just outdated. I wouldn't start throwing rocks from a glass house.
Oh and let's not forget that based on a pure empirical observation of the Linux ecosystem we can see that it is a better choice. And no, noone has been forced to use it(, neither was anyone forced to use Pulseaudio).