As much as I like Discord, I hate that people use it as a replacement for reddit.
It's an entirely different medium that serves an entirely different purpose. Reddit is a message board. Discord is chat. A highly-active Discord is impossible to keep up with, whereas a highly active subreddit is still very useable. You can post a question on reddit, go to work, come home many hours later, and read the answers, and it's easy no matter how much traffic the sub gets. On Discord, if it's very active, you could find yourself scouring through hundreds of messages to see if someone replied to you and didn't use the Reply feature.
It's an entirely different medium that serves an entirely different purpose. Reddit is a message board. Discord is chat. A highly-active Discord is impossible to keep up with, whereas a highly active subreddit is still very useable. You can post a question on reddit, go to work, come home many hours later, and read the answers, and it's easy no matter how much traffic the sub gets. On Discord, if it's very active, you could find yourself scouring through hundreds of messages to see if someone replied to you and didn't use the Reply feature.