For getting technical help, Discord is only as good as the accumulated expertise of the people attending. What happens when expertise moves on to the next thing? Having lived through many “next things” this seems to me to be an inevitability.
It seems to me there is also a bit more tendency towards group-think and herding, not that this doesn’t show up in forums, too.
If getting an answer is as easy as a quick chat, chances are nothing will be written down, and that knowledge will be gone unless someone makes an effort to write a tutorial. With a forum, bad advice has a chance to be corrected or updated. You are more likely to get pros and cons from different POVs contributing to a discussion.
It is fun to hang out with others, and I can see making some nice friendships through that format. It could well be that its healthier to hang out some with programmers and make friends that way. At least, with them (unlike less tech-inclined), you can talk shop. Also, you can spout nonsense (sometimes this is the only way to discover that what you are thinking is nonsense) and not worry about leaving a historical record.
There are a lot of situations where we have a race-to-the-bottom feedback loop operating. I’m wondering if going for ever faster-paced discussion, is one such. There is a lot to be said for “Slow thinking” (c.f. Daniel Kahneman).