As someone who just went through this process, I have to say your knowledge is dated.
My brother (in US since 1991, now a US citizen) sponsored my mom in Aug 2017. Got approval in March 2019. So the process which indeed used to take 4-6 months has lengthened. Along the way they made the process difficult for him, asked for more & more supporting docs (none of which were originally specified). Finally got it through, with the help of a lawyer who charged US$5,000.
The big difference which you don't mention is of course free health care here in Canada. For my mom medical insurance in the US ranges from US$1,000 to US$2,000 a month depending on the reputation of the company and how easy it is to get them to pay up. Which is why there is such a rush to sponsor the aged to come here, of course. World class health care for people who haven't paid into the system.