I'm very much not a Democrat or a Republican, and in many ways I don't give a shit what the Democrats do. But in the vein of "competition is good" and believing that a moderately heathy Democratic party is valuable as a counterweight to oppose the GOP, here's what I'd suggest the Democrats do:

1. Run candidates who are likeable and more importantly, likeable by most Americans. No arrogant "smarter than thou", preachy, judgmental types. Run people who are intelligent and ethical, yes, but with a folksy, down-to-earth side.

2. Drop the radical anti-gun stance and embrace the 2nd Amendment as being just as important as every other part of the Bill of Rights.

3. Stop focusing so much on identity politics. Yes, sure, continue to stand for equality and inclusiveness. But don't make gender politics, trans-politics, race-politics, etc. your lynchpin issues.

4. Reclaim your historical "anti-war party" status.

5. Don't be so abstract. Bring things down to a level that can appeal to the "everyman". Ex: protecting the environment. Don't just talk about "protecting the environment" in the abstract, as though everybody universally values that (even if you believe they should). Instead, talk about protecting the lakes and creeks that people fish in, the gamelands they hunt in, the marshes and bays where so much of our seafood grows, etc.

6. Go more in the direction of the Blue Dog[1] Democrats in general.

[1]: https://en.wikipedia.org/wiki/Blue_Dog_Coalition