It's not pointless at least for the same reason having curtains on your windows is not pointless, and the way you write about 3x3 staircases can be MitM'd, taken other interesting information(bay12 doesn't use https after all), and fingerprinted with same manner of speech but different topic elsewhere, then attacked using either a broad-spectrum exploit (such as packet of doom at crucial moment for an irl attack) or one targeting your system configuration, thus gaining access to your credidentials for purposes at either end-point of targeting your bank account, your computer for mining/botnet/endpoint relay/etc., or further hijacking into otherwise secure systems such as your employers', like employed in Bangladesh Bank Heist of 2016 (attempted stealing of 1 billion, stll got away with dozens of millions) or like how off-the-grid nuclear reactors were inflicted with targeted hidden malware carried on USBs.
Of course, none of that is quite as visible as sending your phone number over facebook messanger and then getting sms advertisements from unknown numbers. "If it doesn't have a gui, it doesn't exist." manner of thinking, this is.
That said, I question the existence of private chat rooms freely advertised as open to the public, which means the main benefit would be forcing an attacker with access to discord data (quite cheaply with a shell advertizing firm) to perform such MitM attack....well, that's assuming you don't have to pay a physical cent to use discord, of course. Last I used it, I didn't, but it's been a few years.
For an averge person, as you aptly demonstrated, this means for migration to happen it has to have functionality in some way superior to discord. Having never used Slack, I'd like if OP could elaborate a little on this point.