Different people absorb knowledge in different ways. Just because you learned the most by reading articles doesn't mean that is true for everyone.

I believe there is value in newcomers/junior devs begin in close proximity with their more experienced coworkers because this greatly improves the chance to talk about important work-related topics. Many times in my live I have started a casual conversation with someone at work and this lead to discussion about current work-related software topics and I was able to share some opinions with someone.

These things happen much more rarely when they are scheduled slack calls, and people seldomly just slack to talk about random things.