OK, my initial response was perhaps a little rushed...and further occurrences on my own game have allowed me to narrow how I can fix it a bit further.
Of course, there's no doubt this is something to do with the presence of a mod, or mods. To me, it seems like something is preventing the rulesets from loading (as I think the other available options cascade from this).
If I am greeted by this issue when clicking on Create New Game, I have to do the following:
1. Exit Civilization VI (to the desktop).
2. Delete the Mods.sqlite file only.
3. Run Civilization VI again.
4. Immediately go to Create New Game and observe that the ruleset has loaded (i.e. you can select your options).
5. After this has appeared, I can navigate back to the Additional Content and select whichever mods I see fit. Selecting all of the mods I want to use in one go works 100% of the time. I have observed that if I select some mods, check on the Create New Game screen, go back and make amendments that the whole thing breaks again.
I'm using a number of different mods, including: YnaMP, PerfectWorld6, Terra Mirabilis, R.E.D for Gathering Storm, Civilization V Environment Skin, Alternative Fog of War, as well as some additional Civilizations. Some of these do indicate non-compatibility (but those simply don't have that field) and once loaded, my game works seamlessly.
Hope this helps!