I don't really get the "let's not politicise this" argument.

Some of the key reasons we elect politicians is that we entrust them with our economic and physical welfare and a degree of faith that they will make the correct judgements on our behalf during their time in office compared with the alternatives.

They are often called to account during their time in office and the way that they manage that crisis often impacts how they are subsequently viewed:

Thatcher was struggling politically but the way that she managed the Falklands Crisis set her on the way to two further electoral victories but then decided that a Poll Tax was a good way to manage local taxes:

Major never recovered from Lamont and Black Monday as we left the ERM;

Blair's aurora vanished when he decided to follow Bush into Iraq rather than listen to the views of his party and the country;

Bush never recovered from looking down on the floods in New Orleans from Air Force 1;

Brown got swallowed up by the 2008 Financial Crisis and regardless of the measures that were put in place to mitigate where most observers thought were correct in retrospect, got swallowed up by the consequences.

Why shouldn't Johnson be judged politically, fairly or unfairly, for how he managed things during his time in office?