It was not classified as serious at the time of older postings back in 2018. It is now classified as serious.
Just to clarify my early points, I never meant it was okay to commit DUI. It is never okay to commit any type of offense whether minor or serious as we all know that is against the law. However, when DUI is viewed through the whole spectrum of criminal offenses it looks minor in comparison. When you put the drunk driver next to a burglar, an armed robber, a rapist, or an arsonist you will obviously see a big difference in the degree of the crime. When you also look at the consequences of a DUI in Canada, the offenders are sometimes given a discharge agreement, a fine and a license suspension, community service or at the very most given a short jail sentence which is usually reserved for repeat offenders.
Canada does bar DUI offenders, even more so now than in the past. You can argue that such people will pose danger to Canadians if they were admitted, which is reasonable, however they also bar people who have forgotten to pay taxes in their own countries or failed to pay child support to their ex-wives in other countries even if these payments were settled and even if it was 10 or 20 years ago and the child has grown up to be an adult and a Canadian citizen. They are not allowed to come for a short visit or even transit through Canadian airports. Canada bars such people not because they pose a danger to Canadians but because they carry the stigma of a criminal record, whatever that may be. Indeed, if you closely scrutinize the admissibility criteria you will find that people who committed criminal offenses, such as DUI and others, and admitted such offenses in court can still be admissible if they had a special deal with the prosecutor to avoid getting a criminal record. So, the issue here is not whether you have been a drunk driver in the past but whether you have an official record that says so.
At the end of the day, the way to make roads safer and lower the incidence of accidents is through strict enforcement. Here in Sweden, a person can be found guilty of a DUI for just having 0.2 BAC level and alcohol itself is highly regulated and can only be purchased from the government in certain times/places and in certain quantities. This is one of the reasons why Swedish roads are among the safest in the world.