Yeah, it's worth it to just start fresh. Keep your user data, nuke the rest and setup from scratch w/automation if it's extremely customized to your liking.

I personally try to use the default config as much as possible so there's not as much to set up after installing from ISO.

There will always be gaps, but describing your machine through Ansible is worth it and can be fun if you're into that sort of thing.

The first time I set up a freshly installed Debian laptop from my existing Ansible roles was a really enjoyable moment.

Being able to establish a familiar base on a fresh system at will is a far greater power than pure config/data backups.

What kind of changes? Package installation, removal and configuration? Use apt-mark showmanual to save list of manually installed packages, dpkg --get-selections | grep 'deinstall$' to save list of removed packages, debconf --get-selections to save debconf package settings, backup files that you edited in /etc. This should be enough for restoration, wouldn't take a long time for backup and avoid risk of filesystem inconsistency.

You mentioned rsync, then take a look rsnapshot if you haven't yet. It is based on rsync and doing incremental backup very well.