Linux

However, systemd makes the system much more secure and reliable as it is

less secure and less reliable day-by-day you meant? systemd introduces needless dependencies ever since as if that was it sole intention ever from its very beginning, which already were used for wide attacks, and exactly those attacks that the people working hard to remove unneeded dependencies for security reasons meant to prevent by things like "do one thing only" (but security was not the number 1 reason for this one i think), systemd instead: 'lets add another level of that exponential dependency tree from the insecurity hell' felt like they did this stupid thing intentionally every month for a decade or more.

and stability... if you don't monitor what systemd does, you'll never know how bad it actually is. i've made custom scripts to monitor systemd's failures (failing in doing a very primitive of its job) and there are hundreds (actually varying around 200 to 300 sometimes more) of such per day on all our systems for one particular(!) measurement only that was breaking service stability and i wrote a measure-and-fix+monitor workaround. other fixes were not monitored however, only silently fixed by workarounds, thus just unnumbered systemd bugs/instabilities in the dark that stole a lot of work capacity...

if you run distros with systemd, unreliability is your daily experience unless you don't really care or have never experienced stability before - like running a service (a single process) for 8 years without any interruption then it suddenly stops and you go like "was it maybe an attack? the process died, how could that be? were there any connects from outside at that moment?" not talking about not updating something that long, but "stability" itself CAN be like if you dont stop it, it'll still run in 10000+ years maybe millions, more likely that humans extincted themselves way earlier than of a process "just dying" by a bug.. while systemd even randomly stops things that were running well for no reason (varying) once a month more or less (also varying in what it actually randomly stops, sometimes (2 times) it even stopped ssh on my servers, me asking myself if i should create yet another workaround for systemds buggyness to not locking me out again from network or ratjer go for the real solution for most* of all systemd problems - *see below) on the few standard installs i personally have as i didn't have the way to automatically replace provider installed distro on VMs in the DC. i want this replacing automatically for the same reason why i don't like systemd, it causes manual work for a thing that should go automated. however due to systemd's perpetuated instability i now managed to have this way, and every second working on getting rid of systemd is worth it 100k times. this however does not solve all systemd-introduced problems as the xz attack showed (a systemd-dependency on xz made the infected xz library beeing useful-for-the-atracker during compiletime of sshd binary with which then the attacker could infect the newly built sshd binary),one could still be attacked through systemd's dependency hell even if one does not use systemd by oneself, but the build machines used for your distro could be affected/infected by systemd's needless dependencies when "also" compiling for systemd-affected distributions thus there is the risk of becoming a victim of needless-systemd-dependencies while not using systemd at all. however the attack through systemd dependency (and that the public solution was not the removal of needless dependencies only included as source for superflous third party "needs") made clear that systemd is an overall problem for security that will not be solved quickly but stay just like all windows insecurities will stay as long as they whish to push them to their "users".

systemd reducing overall security and its unreliability combined with some builtin impediments (i.e. when debugging its defects) is what drove me away from systemd. there are solutions way more stable and way more secure (and way better documented btw) that do not call in for needless dependencies, reducing risks, attack vectors and increases overall debuggability i.e. by deterministic behaviour as an easy example. and none of its important (to me) promises have been fulfilled yet by systemd, drop-in-replacement? have heared that lie thousands of times, but in the last decade i have not experienced it a single time in a distro and it does not seem to be included/finished any more.

for windows users or windows admins a linux with systemd on it IS an improvement in stability, security and of course for updating, yes. but all of that does not come from systemd, rather the opposite is the case, systemd reduces it month by month, thats my experience and thats the most important experience for me, idc what lies whitdepapers tell or what broken promises are believed by anyone or the masses, i want secure and stable servers and services and systemd does not fit in for any of these goals and the time it was still "young" and early problems could be accepted in the hope they get fixed soon are gone, but without those fixes having ever appeared.