"Populist" has been used as a derogatory term for the past decade, but what is it exactly?
It's listening to the population (The popul bit of populist: literally "of the population"), it means exactly whet democracy was supposed to do: have the politicians listen to the people that vote for them.
If populist is being used as a derogatory term, the people using it as such are not democratic. Instead they are authoritarian. Otherwise why would they use it as a slur?
Just remember when people use populist to slur someone, hat they are actually saying is "I support authoritarianism and reject democracy".
That is all.