The most popular games in the world pose an incredibly large threat to all of the other games. When millions of players are online on the same game everyday, that means millions of players are not playing anything else at all. The popular hits hold their players as hostages.
Solo devs are left helpless wondering how they can ever gain a market share. I mean, indie multiplayer online games are dead from the get-go since noone wants to hang out by themselves until another player finally comes along. But there are answers.
The number one strategy is Discord. In your face. A big community button in the main menu, yelling at players "hey, if you want to talk to the devs, other players and generally be our fan, click me!"
We are in an era where people are addicted to online social interaction. There are many potential players who will leave if they can't have that. They will feel alone. Their reaction will be quitting due to instant anxiety whenever they can't share how happy or angry they get for a small little detail.
But game developers not only want them to stay, they need the feedback too. Getting customers to tell them what they think is a win-win. This is how the few succesful online indie games stay relevant. Populated.
Ironically, no means of instant communication is completely unavailable when it comes to any AAA company. If you can't find a community on your own, you're left struggling to fit in. Maybe you can. But if you can't, well, that company has just lost you for good.
Discord is what indie games needed to bridge the gap between them and mainstream. If you like a small-time product by a solo dev, do them a favor and suggest the creation of their very own chat server.
