Forums seem to end up being hostile to newcomers, with all this “did you search the forum first you fucking noob?” mentality. Having a living place for real-time questions and discussion just feels better, same way email exchanges feel terrible after using Slack for so long. You can still have incredibly toxic people in real-time chat servers, obviously, but there just seems to be less overall stress to keep the posts in the forum “pristine” or… whatever that was.
Tbh you can find similar hostility to newcomers in Discord servers, simply swap some words about for a, “Did you read the pins you fucking noob?” mentality. It’s very much the old forum kneejerk response of, “Did you read the rules/stickied posts?” simply in a different context. As you note though, you’ll find assholes in any communication medium.
Also, to your point about a place for real-time questions & discussion, that’s also to its detriment for anyone out of sync with a server’s more active hours, which I think is kind of an understated argument against it among the usual criticism found in these threads. Sure search is one thing, but the asynchronous nature of a forum is imo one of its greatest strengths, especially considering how flaky and/or inundated Discord’s inbox/mentions can be.