Populism is not about ideology of regular people against the elites, that'd be apply more to e.g. various socialdemocratic parties who attempt such goals and ideologies but most of them aren't considered populistic especially if they're in power for years and have to actually implement policies instead of talking about vague results that'll magically arrive.

It refers to a tactic of identifying people who are dissatisfied with current reality and also with the realistic short-term prospects of how future is going to unfold for them even if the promises of the other parties arrive and reasonable economic growth and modest systemic improvement happens, and promising them unrealistic, unachievable improvement (often by suggesting major, radical changes that are a change but can't possibly give the effects they promise) - thus giving these voters hope that others don't, filling that (very valid) need and thus getting their votes.

Populism is pretty much what used to be called "proto-fascism" by Ecco, but communists can also have a strong populist agenda. Where I live, in Portugal, the communist party used slogans like "Leave Nato, away with the Euro" in general elections - simple recipes that couldn't possibly have beneficial effects and that in reality nobody would implement.

What you define as populism has nothing to do with real-world populism, it's just a construct.