My 13-year old son has an absolute blast writing mods for mineclonia with Gemini. He's later e on Diablo-style randomization of weapon drops, rune combinations that cast spells and have effects. And he's even working on what he calls an MMO, but really a server with quests and groups and classes, but probably wouldn't support more than about 16 players.

Great platform for hacking.

Mineclonia is the 'game' that loads into Luanti (formerly Minetest). Luanti has a c++ core engine, but definition of the worlds, rules, games, interactions is all lua

Often kids are playing the game and kids want to play what their friends play and that's most likely not mineclonia.

So first I'd test mods [1] that improve performance. The best thing about java Minecraft is the modding scene.

[1] https://modrinth.com/collection/Dtkcqkms/mods

I'm fascinated with how that game is almost entirely written in Lua.