There is also one huge disadvantage of cron: it requires root. Users can create and run systemd timers without root/sudo.

And quite frankly, your experience is likely due to your personal knowledge bias. Systemd timers are quite easy to debug, in fact easier than cron in my opinion. systemctl list-timers lists all the timers, when they last ran, when they will run next, and you can use other commands to inspect each timer in detail and all associated logs.

In contrast, I find cron much harder to debug. Starting with the first problem, you must first figure out what cron is running, as different implementations have different behavior!