Why can't the daily mail just say "Brexit is making you poor"?
Because it's making the Daily Mail's owners and investors rich, or at least less poor than they would have been if no Brexit. Life is only worse for people who have to care what the supermarket bill is.
Don't forget that for the wealthy, there was a deadline in 2016 that if we hadn't triggered Brexit, various loopholes that allow for funds to be hidden away from tax and scrutiniy would have been targeted by new EU legislatioin. They had to get Brexit triggered before that was brought to bear on all the wealth created in London. For some reason it wasn't in their publicity.