I neither know nor care how many Tourists visit Liverpool, but, as we all know, statistics can be cherry picked to suit just about any purpose, so I'd be taking a very large pinch of salt with thdm.
Well I suppose we can all cherry pick statistics that maybe reinforce our preconceived notion of a place, but I was curious why you found the figure doubtful.
After all a few years ago readers of the travel magazine Rough Guide named Liverpool as the 4th friendliest city in the world.
About the same time, a survey by Trip Advisor named Liverpool as No. 3 in the world, of top destinations to visit.
A few years later a YouGov poll voted Liverpool as the friendliest city in UK, and in 2016 Cruise Critic handed the city the accolade of being UKs best cruise port of call for the 3rd time in 4 years.
In 2018, Trip Advisor named Liverpool one of the top places in the world to visit and the best city in England outside London.
So maybe the figure of 70,000,000 tourists each year isn't an exaggeration.