Populism is where the majority takes the reigns and says, "no, we're not going to do it that way, we're going to do it our way because it provides the most benefit to us, the majority."
In a presidential election, about 60-70 million people vote for the winning candidate out of a population of about 320 million, which is a little more than 20%. That's not a "majority". Those 60-70 million represent a huge diversity of interests and reasons for picking one candidate or another. The idea that "the majority" is a valid concept and represents a group of people with common interests is absolutely ludicrous. The same is true for state and local elections.
Of course, economically, it may seem like you are part of something like "the majority of the bottom 90%" and that taking money from the top 10% and transferring it to the bottom 90% is a good idea for the bottom 90%. However, that is not only unjust, it also simply doesn't work in the long term. It's also not what other progressive welfare states do: European countries finance their welfare states with much higher taxes on the middle class.
"The aristocracy" and "feudal lords" weren't bankers and merchants, they were people who were given special privileges by the church and the state and thought themselves intellectually superior and divinely justified. Then, as now, people like you, Warren, and Sanders hated successful businessmen with a passion, often leading directly to antisemitism and pogroms. And you're right that the hatred of successful businessmen, their denunciation as an "aristocracy", and calls for their expropriation are both progressive and populist; when they become more extreme (usually, after progressives and populists like you have destroyed the economy), they turn into pogroms and overt fascism.
Hayek makes the economic case for why people like you are worshipers and enablers of feudalism in his book "The Road to Serfdom". I suggest you read it.