If rsyslog is no longer needed (mark package install as auto to find out).
Make sure systemd journal is persistent if that is what you want.
Check folder /var/log/journal/*/
to verify.
Then the following old log files can be removed too.
rm /var/log/auth.log* rm /var/log/cron.log* rm /var/log/daemon.log* rm /var/log/debug* rm /var/log/kern.log* rm /var/log/lpr.log* rm /var/log/mail.err* rm /var/log/mail.info* rm /var/log/mail.log* rm /var/log/mail.warn* rm /var/log/messages* rm /var/log/syslog* rm /var/log/user.log*