The coal and steel industries were going to be mullered no matter what, Thatcher just sped up what was going to happen anyway.
UK doesn't use that much coal these days, most of the power stations were switched to gas generation by Tony Blair and the steel industry was archaic. Same thing happened in Germany, France etc. Today the UK makes a smaller volume of more specialist steel.
Even the big coal producing countries do so with a lot less labour than before. In places like Canada/Australia, they can surface mine and produce thousands of tonnes with very small crew. Automated mining has taken off in a big way as well to make it safer and more productive for the guys underground.
Steel too, is has become a lot less labour intensive.
This doesn't mean we shouldn't of looked after our primary industries just what we have done.
We can let all the other countries make the money and borrow it off them, that seems to be working.