The folder /var/log/lighttpd needs to be owned by user www-data too I believe:
pi@noads:~ $ stat /var/log/lighttpd
Access: (0750/drwxr-x---) Uid: ( 33/www-data) Gid: ( 33/www-data)
To change owner for folder and all content in the folder:
sudo chown www-data:www-data -R /var/log/lighttpd
And check again:
stat /var/log/lighttpd
sudo service lighttpd restart
journalctl --no-pager -u lighttpd