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If the UK Labour party had gone the way of other European socialist parties and not elected Jeremy Corbyn, it would by now be in electoral oblivion. Look at the SPD in Germany, until recently still dominated by Schröderites like Nahles and Scholz, or the Parti Socialiste. Both have haemorrhaged support in recent years. (There are obviously some differences around FPTP, which obviously benefits the two major parties, but still.)
'New Labour' was supported by the establishment ('support' from Rupert Murdoch! Thatcher: 'Tony Blair won't let Britain down.'!) because it had subverted Labour and wanted the inevitable change of government without any policies that would adequately balance out what the Tories had done in the 80s and 90s. Corbyn has been attacked absolutely relentlessly and he's still in there with a fighting chance. (I'm not optimistic about the election, though.)
Oliver Schick-
I think SPD is a bit different to Labour. SPD still gets a lot of credit for the economic reforms under Schröder, which are seen as the reason for Germany's strong economy over the last ten years. Their issue seems to be that the CDU has moved much further to the centre and they have lost votes to the Greens. The German far left is not a credible threat anymore, so going that way does not seem like a solution. The SPD just got squeezed in the middle and they were unable to take the credit for their work in the coalition.
In a way Merkel pulled the same political trick on the SPD as the Tories pull on Labour. She was much better at capturing the mood of the country in a catch phrase and pushing her agenda. "Wir schaffen das" drowned out questions about costs and implications same as the three word Brexit slogans we have had over the last three years.
hesa
In the last 40 years all the elections have been won by the Conservatives or Tony Blair. I support Corbyn, but I'm also not mental, so never thought he'd win. But with the chaotic nature of the Tories I'd wager a centrist Labour party led by the likes of Chuka Umunna, or someone else from that now non-existent wing of Labour, would be heading No. 10.