Bingo. In 2008 my wife and I housed and Obama field volunteer for several months who is assigned to the first and fourth most Republican voting counties in Ohio. There are persuadable voters in every Community. You're going to find arguably the same ratio in a 70/30 Republican County versus a 60/40 democratic County. Admittedly, even in the last 10 years things have changed where the name of the game is turn out more than persuasion, but even there there's still the issue of turning out vote the nearly half of Voters who don't show up at the polls but might like your guy.
Organizer never had any illusions of, LOL, winning either County. Our goal was to lose by no more than 40 in my own County, which we narrowly accomplished. You add these numbers up cross 88 counties, and that's what creates a Statewide win. Winning big numbers in Cleveland and Columbus aren't going to help if you get blown out 85/15 in a host of small counties as opposed to 70/30, which is exactly what happened in 2016 and, to a lesser degree, in 2018.
The organiser's argument is the exact opposite of yours: "Republicans win these areas so Democrats shouldn't bother trying with any voters there since they're all deplorable". Her entire complaint is that she was canvassing in a heavily traditionally Republican county and OMG getting Republican talking points on the doorstep!!! and using that to say that Democrats shouldn't appeal to
anyone in
entire county, including those Obama voters who stayed home.
If the organiser had said what you said "we need to try in these places to keep the margin down because there are persuadable voters there" then she wouldn't have made that dumb as all hell tweetstorm about how rural America is deplorable and needs to be sacrificed for fiery lesbians.