I was on EasyJet (U2) recently for the first time in probably 15 years for a trip from the UK to the continent. Having been conditioned as an AC SE for so long, I was absolutely gobsmacked at how much more efficient and stress-free the boarding process on European LCCs can be. I think the gamechanger is the fact that LCCs like U2 charge for "large cabin bags" (ie anything that won't fit under the seat in front of you), and drill into passengers that unless you pay for a large bag, your carryon goes under the seat. They were vigilant at checking compliance as well -- most bags were checked in the sizer, and the priority boarding queue eligibility was enforced. When was the last time you've been on a completely full AC A320 where the overhead bins were only 25% full? It meant that for the return flight, I couldn't care less when I boarded as I knew that I didn't have to rush to secure bin space. Part of the secret sauce was the bag pricing, I think: GBP 39 for a 23kg checked bag, and GBP 33 for a large cabin bag. You could also pay (less) for a 15kg checked bag (but I didn't note the price). With pricing like that, there's much less incentive to bringing your bag onboard. Checked bag delivery at the arrival belt was very efficient on both flights, too.

TL;DR -- Air Canada should take serious lessons from European LCCs on how to make the boarding process more efficient (and pleasant!). I've come to believe that you get what you pay for when you fly, but with AC you're paying more for a significantly poorer service compared to some LCCs.