That's an odd comment to me. Different TLDs have different pricing, different restrictions, and so on. Giving the topic some thought isn't stupid. And .com is a pretty crowded namespace.
Country code TLDs (ccTLDs) [1] often have rules set by the country of origin. These rules vary widely, but some of them include country of residency requirements (you can't buy as a foreigner), ban on pornography, or strict adherence to religious requirements.
Popular domain hack ccTLD .ly is required to adhere to Libyan and Islamic/Sharia Law [2]
(edit because my posting is rate limited: )
There are plenty of non-ccTLDs, though, including thousands of gTLDs.
You can register a .horse domain if you want, and as far as I know, there are no restrictions on use.
Discord couldn't afford to buy discord.com, so they bought discordapp.com. They didn't think of buying discord.io or discord.app or some crap like that.
In the meantime all respectable startups and big companies use .com like normal people.