"You try really excluding systemd from a Debian installation and you'll find ... not a lot of packages that will install."
I guess my definition of "a lot" is very different.
First and foremost, I'm not a systemd fan. That's why I try to get rid of it. I've used it, and when it works properly, it's not that bad. When it doesn't work, that's when it's a royal pain. Things that were once simple to debug become ten times harder because you're not just fighting a simple shell script.
If I am pretty much forced to use systemd (like in Ubuntu Server), I'll disable as many of the "extra" services as possible, like timesyncd or resolved, and use other programs meant for that sort of thing. I still use rsyslog over journald as the primary means of logging.
For my experience with servers, I've been able to run Debian under sysvinit for many years with services like Apache, nginx, Varnish, PHP, Postgres, MariaDB, memcached, node.js, Docker, and all sorts of other very commonly used setups. I'd say those systems are doing "reasonably much".
Is it easier to just run Devuan instead? Probably. I've never tried, so I can't give a first-hand account. I don't know how easy it is to drop in a package built for Debian (most probably work, but I'm sure some don't). If I had to offer up a concern, it would be wondering how long the Devuan guys will continue to make releases. I don't know what sort of financial backing they have to keep them going, so they may fizzle out or they may continue to be a strong systemd-free alternative.