The answer is simple: when I used Debian, I was just starting out with Linux and didn't mess with systemctl at all. It was an ok beginner experience (I'd already used Mint before trying Debian, so I was at more of an intermediate level) but I probably wouldn't like it as much nowadays.
I like the idea of using different software for different things, why do systemd timers exist when there's already crontab, for example?
Meanwhile, I mostly used Arch on my server where I had to deal with all the systemd stuff, which was rarely useful for my purposes.