Have you actually tried to do this?
Personally, I've tried to reform the democratic party from the inside for the last 20 years, and I've given up, I think it's a foolheardy endeavor.
Corporate interests are thoroughly entrenched in the party at every level. The democratic party has set up so many structural hurdles that make it nearly impossible for a progressive challenger to have a shot.
Take a small example: when I was volunteering for two different local progressive challengers, they both had extreme difficulty doing basic campaign things like printing flyers, road signs, pamphlets etc. Why? Because the Democratic Party has a explicit policy of blacklisting any vendor who aids a progressive challenger. No print shop would print our flyers.
There are so many structural hurdles like this set up by the Democratic Party, I would encourage you to volunteer and find out how bad it is for yourself.
Americans have seen a generation of peaceful protests that were crushed and villified. Anti-WTO, Anti-Iraq War, Occupy Wall Street, George Floyd, etc; all failed to achieve any of their stated goals.
And now that the fascists have taken control, peaceful protest is even less effective. For peaceful protest to succeed your opponent must have empathy, and fascists have none.
The last protest movement that accomplished something substantial was the civil rights movement. It was not peaceful, it was militant. I think we need a modern Black Panther Party.