I don't see any particular point in Johnson resigning now, but it's complete nonsense to argue either that calls for him to go are politically-motivated (see, for example, ymb's position), or criticisms are misplaced. This has been an awful year. The Government has been faced with several huge crises. Many other countries are also struggling. None of that is a reason not to hold the Government to higher standards. Firstly, not every country has struggled: you could see the responses in New Zealand, Australia, South Korea, Finland, and several others, all of which has been far more effective, so that that pandemic got this bad can by no means be called inevitable. Secondly, there is a manufactured looming crisis, too, which the Government, at the very least, could have accepted was worth delaying for a little while it focused its efforts on the more urgent issues. Thirdly, demanding that the Government do better is a very patriotic position and even logically follows from getting behind the Government. We should get behind them and help them, as far as is possible, to do even better. Just nodding in blind acceptance should never cut it.
Finally, it ignores the fact that this particular problem is about the personalities at the top and how distracting they are. Again, the crises are hard for anybody, but how much harder to handle when you are too busy fighting amongst yourselves? Cummings' exit speaks volumes about how the present Government isn't able to get a grip on its own petty squabbles, let alone the stuff that matters. We should be angry, to a man, that people at the top are incapable of setting aside such power struggles. And while all that's going on, people here are more interested in laying into the people who can't make a difference? Corbyn is no longer leader. Whatever you think of Sir Keir Starmer, he is a mere bystander. On AnswerBank, none of us matters meaningfully to all this whatsoever (with the notable exception of theprof, who anyway stays outside politics).
Save your criticism about division, then, for the people in power. Their divisions matter. Their inability to cope with the crisis matters.