That's a pretty big caveat you've slipped in there mate.
Look I'm extremely familiar with all the sophisticated justifications for why actually Labour should have gone more remain etc but its just all bollocks. May being weak, Johnson strong, also bollocks. May went into '17 seen as a formidable powerhouse, 100+ seat majority. She was weak in hindsight because labour's campaign fucked her and it fucked her by taking the crown jewel of brexit and reducing it to a side issue and fighting the campaign on everything else where labour policy was better, more attractive, more in line with public attitudes.
Labour in 2017 and 2019 had the same leadership, the same flaws, the same strengths, and while people can bang on about different manifestos as far as public were concerned they had the same priorities and policy commitments. NHS, housing, jobs. The only substantive difference was its brexit position in an election that was all about brexit because labour allowed the tories the chance to make it all about brexit, and the seats they lost were all seats that had a leave majority. No attempts at sophistication can obscure that. You're wrong, sorry.