It might sound unsavory to say that they should drop <issue you think is important>, like climate change, but if that were genuinely the reason they're losing then of course they should drop it. The alternative is you just have a party of ideologues with no power. They can still do good things without doing <important thing>.
I just don't think any issue is as contentious as abortion, or having as much of an effect, because you can hold your nose about a lot of things, but not about 'murdering babies'. Again, this is a moral hard line that a lot of people have. They seriously think that Democrats are ontologically evil because of this; it's far beyond the political. I don't think they need to drop those things you listed from the platform because I don't think it would help them win.
From talking with Republican or centrist or ex-democrat peers and family, some of them would vote Democrat "if they stop killing babies", and others would "if they stopped the racial shit". I've never heard anyone say such a thing about anything you listed.