The problem is that Labour got caned at almost every election from 2015 to 2019 - whether local elections, European elections or by-elections. 2017, not 2019, was the outlier, & even that was a better-than-expected defeat. Treating 2019 as a Brexit-induced anomaly would be unwise
For context: in local elections, Labour polled 31% (2016), 27% (2017), 35% (2018) & 28% (2019), losing over 400 councillors. In the 2019 European elections it polled 13.6% and lost half its MEPs. It lost the Copeland by-election in 2017, for the first time since 1935.
Lab's problems have been building for years & are not all the fault of Corbyn. Critics of his leadership do need to take seriously what happened in 2017. But if Lab convinces itself 2019 was an anomaly, reducible solely to Brexit, it will hand yet more victories to its opponents.
