Factual error: In the warehouse scene with the wooden crates with maple leaves, even though a correction has been submitted saying a maple leaf was valid, the real mistake is the type of maple leaf used. The film shows a modern graphic style of leaf that did not come into use until the 1960s and appeared on the new Canadian flag in 1965. In the time of Capone, the maple leaves used to depict things Canadian looked like actual maple leaves and not like a stylized graphic.
Factual error: The film shows government agent Eliot Ness throwing Al Capone's right-hand man, gangster Frank Nitti, to his death from the roof of the Chicago courthouse in 1929. It never happened. Frank Nitti died of a self-inflicted gunshot wound in 1943.
Suggested correction: The movie was not meant to be exactly like real events. The movie was loosely based on the events (aka "inspired by actual events"). There are a lot of differences between the movie and the real events, these were done on purpose, to make an exciting movie.
That's a lame excuse. There are lots of opportunities to embellish on the truth when dealing with a historic topic. The station scene with the baby is an excellent example of that. But, you can't go changing the relationships of main characters or the time and methods of their deaths. Especially ones so well documented like Capone and Nitti. Why even bother using real names? The character they called "Nitti" was just a completely made up character. Nothing about him resembled the actual Nitti. Nitti wasn't skinny and he didn't wear white suits. He wasn't a loner, often scene hanging with his crew. Nitti was an exceptionally short man with a Chaplinesque moustache. Always jovial for the cameras.
It's simply your opinion that it's a "lame" excuse. The fact is the film is highly fictionalized. It's not a documentary, it's a drama. They combine and eliminate characters, give them different names and characteristics, and show events that never happened. These are not mistakes, they're known as creative license. They would only be mistakes if they film claimed everything in the film was true and accurate to history.
While calling something a "lame excuse" isn't acceptable, the mistake is still valid. The film isn't set in an alternate timeline, so historical inaccuracies regarding real life people are considered valid mistakes. Artistic license extends to adding things that could have happened that didn't impact historical events for dramatic purposes (love interests, made up characters, etc). Historical inaccuracies regarding real life figures would be the same as pointing out anachronisms in a film set in the past, like have a car from the 40's in a film set in the 30's. And just because a screenwriter or film maker wants to change facts to make the film more exciting doesn't mean the mistake is no longer valid.
Might as well toss the whole movie with your logic. Ness was never an active agent and never had any contact with Al Capone. Like already stated, this isn't a documentary, so expect some creative license.
Factual error: We see a British double decker bus on the streets of Chicago. The first Routemaster double decker bus was first introduced in 1956 so the existence of such a bus in the 1920's is impossible. Also, given its UK layout, designed for travel on the left side of the road, any passengers getting off would do so into the middle of the traffic.
Factual error: At the end of the movie, a pack of Lucky Strike cigarettes is shown on Ness' desk. The circle on the pack is red. Before America entered World War Two, Lucky Strike cigarettes had a green circle. The red circle was added with the ad campaign, "Lucky Strike is going to war."
