Modular: good advice. Look at a game like Doom, which survives and thrives to this day because of the open documented WAD format.
Another example is Unity. Despite some of its own shortcomings, the developers made a very open plugin system, and fantastic tools have been developed and integrated into the Unity IDE that fix some of these problems and give it huge amounts of power: ProBuilder (the in-IDE mesh editor) and TextMeshPro (the font dynamic texture system) being two great examples.
Or, think of iOS without the app store, or any OS without third party applications. What's the Lao Tsu saying? Cut doors and windows for a room;
It is the holes which make it useful, etc
Another example is Unity. Despite some of its own shortcomings, the developers made a very open plugin system, and fantastic tools have been developed and integrated into the Unity IDE that fix some of these problems and give it huge amounts of power: ProBuilder (the in-IDE mesh editor) and TextMeshPro (the font dynamic texture system) being two great examples.
Or, think of iOS without the app store, or any OS without third party applications. What's the Lao Tsu saying? Cut doors and windows for a room; It is the holes which make it useful, etc