Minecraft is an excellent concrete example. Simple game mechanics are
conducive to tinkering. Mods that extend those mechanics can be recombined
into functionally new experiences. Many popular Minecraft servers feel nothing
like the original (prison escapes, battle royales, etc.).

However, even Minecraft has a limitation: players can’t contribute new mods to
existing servers. They have to start a new server to introduce changes. As a result,
the Minecraft “universe” is fractured across many parallel, mostly non-interacting
private servers.

There are good reasons that most modern games implement mods like Minecraft,
through instancing (of new servers) rather than scripting (of existing ones). It is
hard to ensure that player-contributed code is compatible with native rulesets
(exploits are particularly challenging). Ruleset updates may break the mods built
on top of them. Limited compute resources need to be rationed intelligently.
The Open Problems of Onchain Games