Chris Siebenmann has some thoughts and opinions on systemd timers. Here's a search query revealing six articles from 2019-22:

https://utcc.utoronto.ca/~cks/space/?search=systemd+timers

>The great advantage of crontab entries in a modern environment that supports /etc/cron.d is that they're much simpler to deploy and use.

I have found the opposite to be true on NixOS e.g. I set up a systemd timer to update ddns every 15 minutes but only to run when the network interface is up.