Reddit used to be open-source, its code still archived on GitHub… then we saw what happened. They closed the source (de facto killing every small Reddit clone) and more recently they cut ties with every developer using their APIs.
I honestly see lemmy.world as a problem. Not as big as relying on Reddit source code, but still a problem. We need to prevent centralization as much as possibile, and one instance having >50% of all users is a bad sign.
Mobile apps (such as Voyager) let you choose the instance you want to sign up. I think they should incentivize instances that are not lemmy.world, until it scales back to a smaller size. Like some kind of rubber-band roulette.