Your question raises the important point that communication involves constant negotiation of different attributes (time, medium of preference, tone, etc.). Those who are good at it will read the room, and sometimes make exceptions so they don't come across as draconian or out of touch.

Did somebody gently redirect you to email instead of Slack when you felt Slack was your medium of choice? You can always respond with, "Sorry, email doesn't work for me because [reasons], please reply here, thanks!"

Everything is a negotiation. Get good at negotiating and these issues become trivial.