Feudalism is a whole social order. Monarchy is not. At one extreme (the biggest role), it means the monarch is (supreme) executive, legislature, and judiciary. On the other, he's just the executive.
And "enough political variety" for what? And for who?
As for betting on genetics: We're not looking at this in terms of monarchy surviving be a good thing, just feasible.
Okay, the other end of the scale... sure. I could see that, because you get political variety from other areas. However, that's just a Constitutional Monarchy, which I concede can survive.
With all that in mind however, I doubt a Constitutional Monarchy would really oppose liberalism, especially considering the other options.
But look, Polish Eagle gave the good reason why Liberalism is trashed, so I guess you're providing the bad reason. I may not agree with it, but I understand it does need to be provided.