The mods are losing. If you search for "reddit gamedev" on Google, /r/gamedev is nowhere in sight, instead you'll see /r/gamedevelopment and /r/truegamedev (which are not private). The "eternal september" effect means that those other communities will quickly surpass /r/gamedev. It's simple internetology.
Simple internetology also dictates that when a site starts making the user experience miserable, users will accrete elsewhere. Discord is actively eating away at Reddit's userbase, to the point where community subreddits tend to be on-ramps to the "real" community located in a Discord, and in my perception the blackout seems to have accelerated this trend.
Discord is a fundamentally different thing than Reddit, and while they can steal some market share from one another, there will always be room for both of them.
Being fundamentally different doesn't necessarily mean there's room for the old thing. Sometimes, tastes just change and people move on to the next big thing.
Of course, it's possible. I'm just saying that we can't ignore the fact that Discord and Reddit are completely different mediums. Reddit is more like a series traditional forums, and Discord is more like a traditional AOL chatroom. I don't see any point in internet history where either of those media have lost popularity.
