How do devs go about creating MMORPGs?

How do developers go about creating an MMORPG game? I want to know how they know what files they should create. Like is there some basic MMO structure for files? I have a vague idea that I’ll have to make a class for level calculation, adding xp, player stats, another for enemy types and spawn rates, and another for player abilities and classes. Is there something else?

I can’t offer any advice for the question at hand. However, I would strongly advise against making an MMORPG if you’re doing so for any reason other than education/hobby as not even AAA studios can get a footing in that space.

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