It's an example of making the worst decisions possible for a multiplayer game (i.e. by not implementing any multiplayer at all) and fixing them anyway.

I'm not sure what you mean by "more complex" because there aren't many games that even reach a tiny bit of the depth of modern minecraft with a modpack like Skyfactory 3. Do your games involve building nuclear reactors out of 60k individual blocks that each have a tile entity (game object) allocated for it? Did I mention that this is just one power generator and doesn't even involve intricate item transport networks carrying hundreds of thousands of item stacks (each of that is a game object) to your manufacturing machines (another game object with completely arbitrary rules)? The machine wasn't cheap. It cost millions of iron ingots and those had to be processed from ore and that had to be mined automatically and the machines that mine the ore were tile entities too. These aren't things that could even possibly run on a game client. Just think about the nightmare of synchronizing such a huge amount of data from the client to the server. You'd need 100mbit upload or more.