Well, fwiw, the only Democrats I ever remember seriously arguing that nonsense were Non-Swing Voter (who turned to Libertarianism lol) and a dingus who wrote a Politico article in December 2016 imploring Democrats to abandon he Midwest in favor of greener pastures in Texas, Arizona and Georgia. Of course, Dems should target the latter two states, but anyone who argues the Midwest is a lost cause for either party is a buffoon. Now, I’ve heard plenty of people describe Ohio and Iowa as Leans or likely R states and advocating for ignoring them Presidentially, but that’s much different than “abandoning the Rust Belt”
A lot of mucky mucks within the party who are directly interested in party resources moving South are quietly making the argument. And one can view the Obama/Trump vs Rising American Electorate arguments (ESPECIALLY the people who draw a strong dichotomy between those two choices as the only options) as a proxy argument for abandoning the industrial midwest to go to the sunbelt and vice versa.
They already have abandoned the midwest by giving priority to anti-gun/anti-cop measures as well as other miscellaneous SJW objectives that do nothing but make Sunbelt billionaires feel better about supporting the Democratic party. All this being done while leaving behind card-check and the public option. The Dems cannot operate as GOP-lite with the added bonus of Planned Parenthood.
Just look at how Dems spit on the face of workers by not supporting coal as well as opposing steel tariffs.