Yeah, why would you want to generate the motd -- the message of the DAY file -- dynamically, through a daily cron job? Ludicrous! That file is supposed to be static!
And that was literally just the opening statement. The rest of the article is also littered with misinterpretations and misrepresentations.
Simple counter-example to your point: other Debian packages who wish to provide information in /etc/motd. The solution to go with drop-in directories (just like /etc/cron.d) has certain advantages over other patterns, but the author seems to be oblivious to all of this.
The author posted the following as the conclusion of the article: remove the symlink, create your own motd.
root@tessier:/etc# rm -rf motd && echo "DO I WORK NOW??" > /etc/motd
> Furthermore, motd is a tool for sysadmin anouncements, not random news from random packages, so autogenerating is not all that useful.
Nobody suggested it was for random news for random packages. Useful examples would be output from smartmontools, unattended-upgrades, systemd or any other sysadmin-relevant package which might perform periodic tasks in the background.
mail -s '<subject>' $(awk -F: '/^<group-name>/ {print $4;}' /etc/group | tr , ' ')
Edit: Besides, the manual does not tell you that simply breaking the symlink will do the desired effect.
Running a set of shell scripts on every login is not the same as generating a file through a cron job. The author is complaining about the former, while you're stating he complains about the latter.
It's would be proper to take care not to misrepresent matters while accusing others of doing it.