No, he isn't. If someone from the outside is influencing the system to preserve key characteristics it has, they aren't subverting the process.
No one thinks foreign election observers sent to oversee contested elections are the heralds of the end of democracy; quite the opposite.
So the example is, depending on how you look at it, either irrelevant or diametrically opposed to the point you offer it to support.
Hence we can distinguish between interventions aimed at subverting the democratic process and interventions based upon reinforcing them.
Whether or not Soros' interventions are enabling democracy or subverting them is a separate debate. My statement is just to show that the premise that 'any' interference is anti-democratic is demonstrably false.
In other words, democracy is a tool, not an end in itself.