Instagram was a Facebook killer until Facebook bought it.
Snapchat was a Facebook killer until Facebook bought a VPN service and tracked every user without consent then stole half its features
I guess you could say LoL is a DOTA killer since its significantly more popular now, although some of that is likely to do with the Russian/Ukraine war
Giving actual compelling reasons to get users on your platform is the only way and the best way and that isn't really a function of time. TeamSpeak, Ventrilo and Mumble got eaten up by Discord and also most game forums
One of the biggest issues with all these stores that are other than steam is that they suck in terms of UI/UX and they are HUGE resource hogs, I am more inclined to kill off the epic games launcher from running in the background because it taking up gigabytes of my system memory and that annoys me