There's a difference between Boris Johnson saying 'the working class are feckless' and then promising policies that they want (on Brexit etc) and then Thornberry, Lewis et al (who've made similar remarks) but promising policies that the working class, by and large, do not want.
I think the 2019 result shows the working class aren't as thick as you make out (Brexit supporting towns voting for Brexit supporting parties) although that's not to say Johnson won't renege on a lot of his promises that he's made to them.
Have you not read the shit Johnson written about the working class about single parents etc? Like I said he is living proof people are dumb enough to believe you if you have the right ruthless **** character. She has it in spades