I agree with the substance of what you said, but disagree with the conclusion. Whether we like it or not, we do live in a low-attention-span country. So, for better or for worse, snappy slogans are what stick, and so must be used. The right snappy slogan, that is.
The other side in a political contest uses snappy slogans to defeat their opponent. Regardless of who you are and what you stand for, if your opponent can succeed in labeling you with a bad-sounding snappy slogan, and make it stick, it is game over. And no amount of sensible discussions minus the self-righteousness will ever overcome that. Most voters just won't hear you over the noise of the slogan, no matter how you modify your tone/content.
So I would say the solution is simple. Fight fire with fire and create BETTER snappy slogans.
What might have happened if the slogan, instead of "Defund the Police" was, perhaps, "Fund Safety and Sanity"? Which is actually what Defund the Police initiatives are about, smarter funding to make communities safer by NOT having the first responder to every single incident be someone carrying a gun, to NOT have the person who responds to a domestic dispute or mental health crisis be someone carrying a gun. "Fund Safety and Sanity." What politician would DARE stand up and declare that they are against "Fund Safety and Sanity"? If that was the slogan that Democrats in rural areas had wielded against Republican opponents, and made it stick,....game, set and match.
Democrats, progressives, you have all the policies that a majority of Americans would want and support. Hire a PR/Ad firm to "sell" it. That is the only realistic way forward in our world of the 10-second attention span.