Moreover, the "finitude" of the world can be mitigated by the fact that Luanti also offers 64 km total vertically out-of-the-box; various mods use this space to create the equivalent of "dimensions". In practice, without tools that allow to dig ridiculously fast, supposedly realistic mountains (what can be realistic in a game where you can carry with you several trees, casually jump 1 m anyway and barely get a scratch from a 15 m fall?), planes, dragons or whatnot, a "troposphere" of 1 km is plenty, and would allow 128 64x64 km "dimensions".
That being said, and my own biases put aside, people outside of the Luanti core team are working on that [1]