because it paints the view that the country was pretty screwed up before thatcher got in, which is pretty much against the picture you are trying to paint.
You need to stick to facts mate, not make stuff up to suit your agenda.
The UK was screwed up before Thatcher’s premiership, I am hardly going to suggest otherwise. Average growth in the 1970s iirc was 2.4%, mass unemployment had rocketed to 1.5 million, there was widespread resentment at totally unjustified government wages policies, and so on.
Thatcher, like a true Tory, managed to make a bad situation worse, much worse. Exactly the same thing is happening now, ie, no one can pretend that the present Tory government inherited a particularly healthy economy, despite taking over an economy in growth, but they have now made the situation even worse and the UK is back in recession.
Of course none of this actually matters to the present government because like Thatcher, however much they screw up the economy won’t matter, as they will have achieved what they intended to achieve.