I think making it as easy and feature packed as the big commercial apps and services would go a long way.
Right now asking someone to switch to a more private service/app is not only the work of switching over, but also learning an often much more complex system.
Sync is mostly for bookmarks, history related stuff, and a few sparse settings. But it doesn't sync a ton of stuff like customization, addon settings, and so on.
I generally just use latest for most services. For critical stuff I pin the major version number. Also anything that doesn't gracefully handle major version updates like Postgres and similar.
If something breaks I fix it, or restore from the nightly backup if I can't.
Basically a backup is a point in time snapshot that you can restore from. So you'd run backups daily or multiple times per day and can easily get back deleted or changed files.
Whereas with a sync service if you delete that file or change it, the original is gone and you can't get it back. Some will have versions and trash cans, which gives you some limited ability to restore.
Adguard Home has been absolutely rock solid for me, and it offers DoT and DoH servers so you can easily connect devices over those protocols if you want to.
You can do it with any router by manually configuring devices, but one that lets you advertise the PiHole IP as the DHCP DNS option makes it a lot easier.
People will rent them for the right price.