In my experience, I like IRC (been using it for ~10 years), but sometimes there is a lot of noise. For example, the Angular.js IRC channel devolved into a flood of bad questions with not enough information to help, and some entitled users. Many in the Angular community ran away to Slack in response. Code snippets aren't as nice either in IRC vs. Slack.
I'm not sure what the solution is, but IRC is lacking (and sometimes blocked at workplaces) & Slack seems to solve most of the issues, but it not wanting to support large open source communities is an issue as well. There is a hole in tools available.
I'm not sure what the solution is, but IRC is lacking (and sometimes blocked at workplaces) & Slack seems to solve most of the issues, but it not wanting to support large open source communities is an issue as well. There is a hole in tools available.