I don't want to be rude, but I don't believe you. I also have seen the polling and the country does not believe it as a whole. Democratic voters also don't believe it either. If you personally have an income >150K you are likely completely insulated from real Americans. The perception is that the Democrats care more about Israel and their donors than the country. Only 8 percent of Democrats are supportive of Israel but almost 90% of Dem senators are (I made this number up, the rest are real).
edit: the Republicans are publicly grifting, lest you think I like the Republicans. My overarching point is that ~60% of American's don't own homes and are completely uninvested in this country. They have completely given up, or are in a state of giving up. The Republicans and Democrats are extremely vile reptilian grifters who sold out this country.
There were great campaign finance laws on the books, but Republican-appointed judges have steadily eroded those over the years, culminating in Citizens United. We have to overrule that awful case if we are to ever have working campaign finance laws in this country again. There's only one way to overrule that case, and that's with Democrat-appointed judges. Those judges typically do not answer to donors and so don't have the same incentives you've identified.
I really don't think that the Democratic establishment as we know it has much time to live. Democratic voters are not interested in the center-right. They want to go left. Candidates that move things to the left do well without expensive campaigns.
For the majority of the problems I see that I believe the government should be addressing, one side says "that's not a real problem" and the other side offers a really bad solution that they also won't realistically be able to make law.