Historically based movies often take some creative license with their stories and their characters. The movie Churchill takes this to an extreme that significantly distorts the historical record. Set on the eve of D-Day in June 1944, the movie revolves around Churchill's last-minute opposition to the Allied plan for the Normandy invasion. In fact while Churchill had expressed real reservations about a cross-Channel invasion earlier in the war, he had certainly become a supporter of the plan by June 1944. Indeed, the screenwriter, historian Alex von Tunzelmann, has acknowledged that she "telescoped" Churchill's opposition from earlier in the war into the days just before the invasion. Besides distorting the history,what this does is make Churchill seem at best ridiculous.
Of course, there was much in Churchill's character and way of operating that deserves to be examined more critically, without the aura of heroic greatness that has understandably enveloped him. (The portrayal of an even older Churchill in Netflix' The Crown, for example, certainly fits into that category.) But, it is one thing to pay greater attention to Churchill's personal peculiarities, his depression, his drinking, etc., and still be faithful to historical truth.
That said, the movie is still worth seeing. For one thing it does accurately depict some of the other high drama that preceded D-Day. This included Churchill's scheme to sail along with the invasion himself - something that the King himself had to intervene to stop him from doing. And the movie does depict effectively the stressful last-minute decision whether or not to count on a predicted break in the weather and go ahead with the invasion. That decision was Eisenhower's, of course, and the movie does a good job of portraying how stressful the decision was and ultimately how Ike took the responsibility to make the fateful decision.
Duty and responsibility are central themes in the film. Two characters in particular, Churchill's wife Clementine and King George VI are depicted - excellently - as both embodying those qualities and together calling Churchill himself to a fuller appreciation of how those qualities are to be best practiced in his wartime role. The movie actually does a good job of highlighting the differing challenges - indeed vocations - of political and military leaders and the importance of appreciating those differences in practice.
The basis for Churchill's alleged opposition to the invasion in the film is his recollection of the carnage of World War I - especially his own role in the Gallipoli disaster - and his resulting revulsion at the idea of sending so many young men to die in a militarily problematic strategy. These are not in fact inappropriate considerations. They do deserve to be raised when discussing military strategy. One only wishes that the movie might have had Churchill voice these concerns in a compassionate way which did not exploit his character flaws to make him look foolish and even deluded.