Don't take this the wrong way, but I feel like only someone who really appreciated MM would understand. As you said yourself, you didn't play the gamemode. With more development and bug fixes, it can be even better than it was. The fact that you could expand the small cube/island/thing into a massive map was wonderful. You aren't restricted by the square boundaries of a plot. Next, there's the personal option of "intense server activity." Basically, turning off block updates (for floating sand, carpet, weird world edit stuff, etc.). This was possible because each creative cube was like it's own little mini-server, if that makes any sense. In a plot world, everyone is in the same "world," so messing around with block update stuff/intense server activity isn't as flexible. Next, there's the TMD presets. Those were great for making your own stylized build of an already completed build (Alexandria, Prison, and I think Woodbury? Don't remember the specifics, I never used the presets). This made Role-Playing fun, and you could add your own twist to the current TMD. Next, the freedom of making the map as big or small as you wanted. With plots, it's still restricted to some degree, but with the MM worlds, the possibilities were endless. Also, the void-world option was perfect for making space themed builds and floating castles, etc. With a plot world, large scale builds all smashed into one place gets kinda messy. Another awesome thing about MM was that you could choose a texture pack for your world (so those who visit it would download it, kinda like how when you log onto TMD is auto-downloads the pack), so it could be the MW, TMD, or Vanilla texture pack. Another important thing: MM was one of the sole sources for the build team to find new recruits.
In conclusion, Map Maker was a much more unique and versatile creative world than regular old plots. Besides, if you wanted a plot world, just go over the AJ Gaming or Cube Creative or something.
