What your argument is describing isn't populism in general. Trump's populism is christian nationalism which seems to be what your argument is referring to. Bernie's platform in 2016 and 2020 was a populist platform that was intended to forward a progressive agenda.
https://www.wordnik.com/words/populism
A political philosophy supporting the rights and power of the people in their struggle against the privileged elite.
Why would we discard it later? Populism isn't inherently radical or reactionary as Bernie and Trump have demonstrated. It provides a narrative to contextualize what the campaign is for to the people. Which Democrats definitely needed in this election. It's highly unlikely Democrats will make their own populist campaign. We need to hijack the Democratic Party the way Bernie tried to do and Trump did to the Republican Party.
The strategy is to use the Democratic Party so we don't have to build our own party from scratch. It's not because we like or think highly of Democrats. Because of our first-past-the-post voting system we end up in a two-party system. The Democrats are the tool we have to use when the Republicans are fascists that want to kill us.
There has been some progress in this regard. So it is possible to change systems.
https://en.wikipedia.org/wiki/Ranked-choice_voting_in_the_United_States
These aren't mutually exclusive. Humans are imperfect. The systems we build are imperfect as a result. People have been measuring democracies on a scale from 0 to 10.
https://ourworldindata.org/grapher/democracy-index-eiu?time=2023
The US was made by wealthy land and slave owners. The compromises in the document reflect that. After WWII, McCarthyism did a lot to undermine communism, socialism, and the left in general in the US. It laid the ground work for the neoliberals who would come later to fill the minds of Americans with their ideology. The right in this country has been working to undermine the left for a long time. Blaming everything on democracy really misappropriates blame here. Especially when it's Republicans who have been working to undermine democracy.
Things only get better by making them better. What accelerationism misunderstands is that things haven't got better in the past because bad things happened to people. It's that things have gotten better because people learned from the bad things that happened to them and then used that knowledge to make things better. If we let things get bad and no one learns anything, it won't do any good. We have to educate people. And we can do that without things getting worse.
As it is now we might learn a lot of lessons from the rise of christo-fascism. But we may not be able to act on them. These election results have truly fucked us. Fascists might end up killing us all with fossil fuel emissions. But of course billionaires will survive in their apocalypse bunkers.