This is impossible until a critical mass of voters across every state starts putting competence and integrity ahead of their pet issue and populism. If you actually want to start making headway in this direction you have to stop voting for candidates in either of the main parties. The parties are probably not salvageable. Find a third party candidate with these qualities and vote for them and convince as many people as you can to vote for them.
If we can't do that then we are just stuck as a body politic.
A both-sides guy! How original!
Choose the worst Democratic politician currently in office and please explain what they’ve done or said that is in any way comparable to what the Republican Party is doing.
Realistically, the option that will actually work for you is to fight within Democrat primaries. The absolute best case is you get a Mamdani. (Note this means accepting a bit of populism, because ultimately it's a popularity contest). Third parties are going nowhere due to the coordination problem.
(NB: this is meaningfully different in the UK which has really multi-party elections despite Westminster elections being FPTP)