*In fact, Charlie Kane is a portmanteau of Hearst, Chicago tycoon Samuel Insull and Howard Hughes certainly, Susan Alexander is much less the talented, charming and successful Marion Davies than Insull’s debatably talented wife Gladys Wallis. None of which answers why this hapless schlub is the central character and not Welles or Hearst or Marion Davies. Oldman's big Oscar Moment, where he drunkenly conjures the entire plot of Citizen Kane to Hearst's dinner party at San Simeon, is an embarrassment (made more so when Charles Dance comes back with a monologue of his own, delivered in that actor's patented understated menace). Gary Oldman on his best day couldn't do much with this character, and this is far from his best day he seems completely adrift, flailing about to find a point of entry into Mank's psyche that the script couldn't provide him. Apparently he draws attractive women to him like moths to a flame, though heaven knows why.
He's wired into the Hollywood movie machine but we don't see any evidence of why, except that he makes people laugh (Mankiewicz was, of course, not only a writer but a producer in real life, and not just some glib hanger-on). He's a crabby, witty souse who's apparently a great writer, though we don't get any firsthand evidence of such except a few out of context lines from Kane. Mostly though, Herman Mankiewicz is never interesting enough to justify hanging the story around him. Except to claim that Mankiewicz’s (fictional) guilt over Sinclair’s defeat motivated him to write Citizen Kane, which, no. And considering how much time Fincher spends on Upton Sinclair's botched gubernatorial campaign, he treats it in such a superficial way (all to make an oblique comment on Trump and "fake news"?) that you wonder why he bothered.
I was thrown early on by characters talking about The Wolf Man (1941) in a scene set in 1930, and there were similar minor-but-annoying errors sprinkled throughout the script. The historical inaccuracies aren't particularly egregious (fortunately, there's not enough Pauline Kael nonsense to really complain about), though perhaps it’s time to dispel the myth that Hearst was the sole inspiration for Kane.* Still, there is a lot of carelessness that makes what should be a movie buff's delight hard to swallow. But it's also sloppy and sluggish on a script and story level, something that no amount of retro-flair can disguise. It's competently made on a production level, with a convincing evocation of black-and-white cinema, and there are some solid supporting performances: Amanda Seyfried as Marion Davies, Charles Dance as William Randolph Hearst, Sam Troughton as an impeccable John Houseman. Mank, final thoughts: it's good that my expectations were low enough that "not completely terrible"="better than I'd feared." Still not a very good movie, though.