Labour can’t realistically make this a ‘pseudo-referendum’ on Brexit. It would look farcical them taking that approach because of the divisions in their own party on the subject. Nobody thinks Corbyn is enthusiastically pro-EU - McDonnell even less so. They were so anemic with their support for the Remain campaign that such a stance would not be plausible.
The Lib Dems will certainly run almost entirely on an anti-Brexit platform. They should make significant gains (especially in Cornwall and the West Country) but its hard to see past a Tory increased majority.
I agree that Labour cannot realistically turn this election into a pseudo-referendum on Brexit. I do think it’s likely some people are likely to try to do it, though.