For example, atm I need to have 3 services. Two of these services need to run at the same time, they can run separately but then they are not useful. The third services can only run with both services online and is first run 15 minutes after boot (not earlier!) and then every hour but the hourly run MUST NOT run before the first run of the boot (ie the very first run may happen 15 minutes after boot, even if the hourly run would have happened in that time, it cannot)
This is not trivially achievable with cron and classical init other than resorting to complicated shell scripts in both.
With SystemD I can cut down on the complexity by declaring this dependency in the service files and the timers in systemd are sufficiently configurable to achieve what I need.
Sure, systemd isn't flawless, but it's a mile better than the average init script I'd have to hack together otherwise. Journald isn't pretty either but with the right configuration you can cut down on the lag.
And before systemd problems like the above wouldn't have errors in specific lines either, some shell script would be subtly wrong and the entire charade would collapse in an instant.
You don't have to think about systemd at all. Ansible and other modern tooling can abstract managing the machines for you (atm I managing about 200 VMs in Ansible playbooks and it works great)