To be fair, the question of whether it’s historically accurate is irrelevant because the film obviously doesn’t depict real events with real cardinals… even to the viewer who knows nothing about who is who in the real-life Catholic hierarchy, the terrorist event that triggers a major plot twist should be a big clue that this is a fictional thriller, not a documentary. Apart from that, the setting is contemporary so history has nothing to do with it.
So it’s a gossipy political thriller where the setting is the Vatican, not the White House or the House of Lords. The question remains: is it a reasonably faithful depiction of the way a real papal conclave operates, in both procedure and the negotiation/clique-forming/decision-making process? Catholic friends of mine who know much more than I do about what goes on in Rome actually have the opposite fear: that it is all too realistic and exposes too much about the power games that go on instead of earnestly seeking the good of the faith, and of the faithful. If that’s the case, then in the long run it can only be good because, as Christ Himself said: “you shall know the truth, and the truth will set you free.” (John 8:32)
Edit: to be fair, there are some flashbacks in the film to historical events taking place in Latin America, IIRC these are also fictionalized but yeah, I could imagine someone who knows the history of that particular situation being able to say that it's innacurately depicted; however that's not the key theme of the film's narrative, which is a contemporary papal election. By contrast the film "The Two Popes" does deserve the historically-inaccurate tag, because it depicts a meeting between two real-life people which definitely never happened and is purely the imagination of the playwright who asked himself "what if?" In that case, I do wish that the film would preface itself by making it clear that it is purely a flight of fancy in order to explore ideas around faith, theology and succession because I'm sure a lot of people really do believe that Francis did have private conversations with Benedikt and received his endorsement.