I can’t say that Murray as FDR was the worst movie casting ever, because I will shortly point out some worse ones. The Times ducked responsibility for those because of the “recent decades” qualifier. Ironically, one of Oscar’s Best Actor nominations this year meets my definition of incompetent casting: Ethan Hawke is nominated for his portrayal of lyricist Lorenz Hart in “Blue Moon.” Nope, sorry, by any rational measure, casting Hawke as Hart makes as much sense as casting Melissa McCarthy as Marilyn Monroe. Hart was less than 5 feet tall. Hawke is a fine actor, but he’s 5’10.” Not only was Hart tiny, but his short stature played a large part in his life-long insecurity and emotional problems. Would you want to see Danny DeVito play Lincoln? Would you cast Jared Leto as Orson Welles? Tom Cruise as Martin Luther King? The only excuse for casting Hawke regardless of his height is the assumption that most movie-goers today don’t know Lorenz Hart from a Type D battery. Relying on your audience’s illiteracy and ignorance—and then adding to it, as in representing Lorenz Hart as normal sized— is unethical.
I will now note some other unforgivably bad casting choices that top all of the examples on the Times list. Sadly, the two worst involved one of my favorite actors, John Wayne. In a weak moment he let Howrad Hughes talk him into playing Genghis Kahn in “The Conqueror.” Everything about the movie is Ed Wood-terrible, but none worse than the Duke playing a Mongolian….
Nevertheless, the great George Stevens arguably equaled this casting botch when his 1965 all-star production of “The Greatest Story Ever Told” featured the Duke as a Roman Centurion at Jesus’s crucifixion.
It’s arguably even worse casting because the Duke’s appearance in such an alien setting and in such a solemn moment comes as such a shock; it would be as if Wayne showed up in “Snow White and the Seven Dwarfs.”
There are other older casting disasters, like Cary Grant, romantic leading man par excellance, being cast as Cole Porter, who was famously gay, and when Steve Martin starred in a grim, dark fantasy he didn’t have the chops to handle, “Pennies From Heaven.” Francis Ford Coppola’s nepotism-based decision to cast his non-actress, charisma-challenged, big-nosed daughter as the romantic lead in “Godfather 3” was both cruel and stupid. As the Hollywood musical slowly crashed and burned like The Hindenburg, several casting decisions have been terrible, such as Tim Burton inflicting Johnny Depp on Sondheim fans as Sweeney Todd, and Russell Crowe being cast in a crucial singing role in “Les Misérables” despite being unable to sing at anything approaching a professional level. The unforgivable choice to let Marlon Brando’s thin, unpleasant singing voice ruin the film version of “Guys and Dolls” will live in infamy. Nothing, however, approaches or will ever approach the Duke’s two disasters, or the horror of Bill Murray portraying FDR.

really hoping you had a gift link for that story.
-Jut
Oops! It was supposed to be…I fixed it. Gift link now…
An inverse of your Ethan Hawke/Lorenz Hawke situation could be 5′-7″ (or maybe less) Tom Cruise cast as Jack Reacher (6′-5″ and imposingly bulked-up and buff, per the books).