One can, and I will.
We have two mountain-based Civs and one mountain based leader, all of whom base their entire game plan on a coin flip. Ignoring Pachacuti for a moment (who gets the worst of it- his abilities give him nothing if he has no mountains), the Civs are also dealt a bad hand by the map generator.
I've seen a fair share of mountains, but the number of them varies wildly from game to game, resulting in a lot of games where it makes no sense to pick Inca or Nepal at all. And that's a shame! Those two turn into wasted or "dead" Civ slots for players, which is especially egregious for a DLC Civ.
Anyway, just for fun, let's be methodical about this. How dependent are Inca and Nepal on Mountains exactly? I did the math.
Counting their Civ ability, individual tiers of civics, policy cards, and their unique units and infrastructure as one "bonus" each, the Inca lose 6/12 of their bonuses with no mountains.
Using the same method on Nepal, they lose 9/14 of their bonuses with no mountains.