The thing is, it isn't. The UK is a left leaning country economically, and right leaning socially. The Tories understand this, that's why Johnson has been nudging them left economically ever since he came in, it's why he's been nicking ideas from Labour like raising corporation tax and increasing borrowing, and it's why more traditional conservatives focus so much on culture war bullshit, because their views on the economy are unpopular. Even if the Tories are lying about what they'd do economically, they're still at least trying to appeal to people.
The problem Labour have is that those that wanted Corbyn out are essentially the inverse of the public, right leaning economically, left leaning socially, appealing to a secure middle-class that can occupy itself with more fringe issues that as whole the electorate doesn't care about (Honestly, me, if I wasn't so tied to my left wing economic views). So they see what was actually popular about Corbyn, say "that won't do" and chuck it all out, then are shocked that no-one in the country resonates with them. It's nothing to do with progressive parties putting aside their squabbles, Labour needs to get out of it's bubble, realise it's not the 90s anymore and actually engage with people on a local level and understand the issues facing the country. At the minute the party stinks of a smug "I know better than you" attitude for basically every position on the political spectrum, if they can shift that attitude and start putting forward ideas to actually improve the country, there's no reason they can't turn it around. But it will never happen if they straight up refuse to learn the lesson that has been smacking them in the face since the EU referendum, which is stop ignoring the working class.