I'm not quite sure who you think Labour are appealing to though. There may not be a stop Brexit button, but there sure as hell should be a structured opposition to a hugely damaging government policy, and that opposition should be remain - a position Labour themselves campaigned for. Them taking a stance on this would demonstrate far more clearly that there are consequences to Brexit that are seriously worth opposing, and give Remain a force to rally around. Moreover, it will win them far more votes in any GE than their current position, which has them struggling to stay ahead of the Lib Dems. I mean fine, give the Tories what they need to be able to paint Labour as Remain - what fucking consequence is there to that now? Labour have lost everyone they're going to lose to this issue full stop - so choose a fucking side! Try to win back the 14% of lost voters who went for the Brexit Party, or try to win back the 50% of voters who went for the Lib Dems.
There is simply no good logic for their stance, and it is clear to me that they don't have the stones to take on Brexit properly, and simply want it to go away so they can focus on their other policy issues. They're fucking useless.