I have been using Zabbix to monitor my servers for the last years, since I wanted something simple and this Grafana/Prometheus stack always scared me because, as the OP says, of the amount of “moving parts”.
Zabbix has been quite solid and has lots of templates for different servers (linux, windows, etc), triggers and can also monitor docker containers (although i never tried that).
The only thing Zabbix cant do well is log file monitoring, so I am considering something like an ELK stack as an addition.