Obviously have never attended one, but I sometimes witness these matchmaking meetups (dinner/lunch…) from a nearby table.
Today, I was unlucky enough to be next to a “large scale” 合コン (Goukon) of about 12 people (6 men, 6 women). It was loud, it was annoying. Each of the men trying to be funny and loud and show how great he is with the women doing the same. Does it really work ? probably it does. When going on a date (after the goukon), one can see the real character.
But what do shy introvert people do ? Change their character for a day, or just lose the girl they like.
At some point, I wanted to go to the next table and tell the men how lame they look from aside, but obviously I did not. They can be lame, loud, try to impress the girls and hope for a date with the girl they like.