Really depends how you measure the economy. Gross national happiness seems like better way to judge the health of an economy than GDP, which has little bearing on the state of most people's lives.
Humans make all this shit up, line goes up is a completely valid retort to how the economy is being mismanaged, because it is what is seemingly most important regardless of the quality of people's lives.
Saying if the line didn't go up, people's live would be worse is true, but only because of who we are letting rule the playground, i.e. if they don't have all the toys then nobody is getting anything.
This is just project fear, why would the Tories want to asset strip and destroy the country they live in, just for temporary gain.