Got to say Mountain Climber I think this is entirely backwards.
The problem isn't that Corbyn's Labour were obsessed with representing "fringe concerns, minority 'PC' issues". It's that the section of the working class you're talking about have become obsessed with attacking "fringe concerns, minority 'PC' issues".
Corbyn's Labour throughout 2015-2019 were offering a pay rise for public sector workers, collective bargaining for trade unions, and 4 extra bank holidays for the home nation's saint days. What are those if not working class gains? It's 3 policies directly giving workers more money, more power, and more time.
Half the working class have stopped caring about any policy areas that'll actually affect their lives. All they're interested in is deporting immigrants, Meghan Markle and where trans people go to the toilet.
Edit: I may be overstating it to say the working class have stopped caring. But I do think a certain amount of knowledge or skills has been lost since Thatcher gutted the trade unions. I bet a lot of voters in their 20s or 30s wouldn't know what collective bargaining was or how it could help them.
In fact there's probably something in peoples understanding of politics reducing over the years, and these same people finding an elitist patritional government appealing.