Since the purpose of this jam is only creating a level, could someone submit one made using Mario Maker? It truly does focus all of the creators abilities into just one thing - level design.

This is just my two cents, but if you're designing a level using pre-made props, obstacles, and enemies that are all designed to work with specific pre-built gameplay, you haven't really participated in a game jam. I'm sure you have to submit here on Itch, so Mario Maker would be out anyway (I'm not positive, to be fair), but I'd personally see much more value in your project if you teamed up with someone who was developing gameplay and did the level design for their project. Someone was in just such a position in Discord. Again, that's just my opinion, and I'm not running this thing.

Thanks for the question! Yeah actually as DavidA3D mentioned it would probably be best to find maybe a teammate or a template but you do bring up a good point,  Mario Maker could be helpful if you wanted to make a level and then recreate the layout in the template, I think that could work well actually! Here's a little step-by-step tutorial that could be helpful too: https://mozdevs.github.io/html5-games-workshop/en/guides/platformer/start-here/
I hope that helps and best of luck!!!