As HackedToaster said, AIF is becoming much more important now than it ever was. Think about it this way: assume the highest possible average you can have is 100%. Then for a program with an admission cutoff of 90%, many people can get in solely from having an average at or higher than 90% without the AIF even needing to be considered. Now, if the cutoff is 95%, that only leaves a 5% margin between the program cutoff and highest possible average attainable. Coincidentally, the AIF can add up to 5% to your average. So it becomes a lot more possible for people with lower averages ranging from 90-94 to get in with stellar AIFs and also leaves the possibility of people with 95% averages and AIFs that add nothing being denied. Ie. since there is a smaller window of improvement possible in grades, AIF matters more. That being said, SE had a cutoff close to 96% last year and it'r presumable close to 97% this year; there are people in the 2020 page who said they were denied this year with 96% averages. So this all adds to the AIF being even more important than it ever was. Furthermore, the university itself states that they don't see a clear correlation between first year success of students who came in with low 90's averages and students who came in with high 90's averages. Many low 90's students maintain a 90+ average in first year and many high 90's students drop all the way down to 60's-70's. Ideally, I think it's time for Ontario to start using some sort of standardized testing like other provinces use because this problem will only become more apparent in future years. This isn't such a big deal in the US since:
They have standardized testing
There are many more (good) schools in the states than in Canada which means if you don't get into X Ivey League School, you might get into the next best one which is practically the same in terms of prestige/ranking.
In Canada however, if you don't get into UW CS/Engineering, arguably the best school for undergrad because of co-op, your next best thing isn't anywhere nearly as good.