You can have both. One doesn't invalidate the other.
Forums are no different from instant chat apps like Discord, in that, once you reach a certain size, you'll stop being able to stay on one topic most times, unless you heavily moderate and people hate that more than conversations diverging from topics(speaking from experience in both sides). But they're also great to engage with strangers and a wider amount of people at all times.
The main issue is that one is instant messages and the other has a delay that could be hours or days even, since people aren't going to wait there for someone to reply. The instant messages have a similar problem, in that, it can be hard to follow a conversation once you reach a certain size with comments flooding the chat and comments are mostly lost (there's the log, obviously) unless you're willing to go back and read everything. Discord and similar apps, are great to engage with people who are regulars, since you're already acquainted and can have a more casual and faster conversation.
They both have their positives and negatives and there's no good reason to not use both.
Forums are no different from instant chat apps like Discord, in that, once you reach a certain size, you'll stop being able to stay on one topic most times, unless you heavily moderate and people hate that more than conversations diverging from topics(speaking from experience in both sides). But they're also great to engage with strangers and a wider amount of people at all times.
The main issue is that one is instant messages and the other has a delay that could be hours or days even, since people aren't going to wait there for someone to reply. The instant messages have a similar problem, in that, it can be hard to follow a conversation once you reach a certain size with comments flooding the chat and comments are mostly lost (there's the log, obviously) unless you're willing to go back and read everything. Discord and similar apps, are great to engage with people who are regulars, since you're already acquainted and can have a more casual and faster conversation.
They both have their positives and negatives and there's no good reason to not use both.