Pure?

In perek Hay, Yeshiyahu recieves a vision from God. He acts as if this is the first time he has ever seen G-d. He says, " Woe is me, I just saw G-d and I am impure and I live in a nation that is impure. In the Pasukim He gets purified by and angels who take hot coal from the Mitzrach and touched the coal to his mouth . After he is purified he volunteers to go on a mission. In my opinion he needed to be purified before he could go on his mission and the coal is like making him a navi.
      In todays time, people g to mikvahs and become purified all the time. Jews are still not pure but you become pure once you go to the mikvah . This is just like Yeshiyahu getting coal to his mouth because now he is pure and a good jew. But he isn't forever.