Trudeau was always an empty suit with empty-headed ideas (or really just no ideas of his own at all). The amazing part is that he's lasted this long, which is more an indictment of the conservative party in Canada and perhaps the average Canadian voter's love for shiny, polite things than anything else.
I'll never forget one of his early press conferences after taking office when a planted reporter fed a planned question about machine learning to an expert at the mic, and Justin stepped in with an "I'll handle this" and went on a long, and clearly memorized, detailed explanation of the intricacies of the tech. The press, naturally, gushed and goo-gooed over how brilliant he was when it was painfully apparent to anyone with a functioning brain that he had no clue what he was talking about. In short, he has always been style over substance, has gotten by on charm and saying the right things that make most Canadian voters feel warm and fuzzy, all while adding zero value to the country, and has now overseen the worst Canadian economy in most living people's memories along with the immigration issues already discussed above. He's overseen serious cultural instability and economic misery, and now there are loads of angry voters who would ultimately prefer a left-leaning moderate but will likely vote far right in the next election just to send a message to the liberal party (sounds a bit like another country we all know well).
As noted above, the immigration issues are no doubt part of the dissatisfaction with Trudeau, but as is most often the case, the economy is the real issue. He has been a big spender and doesn't see a far-left pet cause he doesn't like to throw money at. His ousting stepping down has much more to do with taxpayers' dissatisfaction with government spending when they're struggling personally than it does with immigration. When you factor in how much the government, particularly in the Eastern half of the country, handled the pandemic and the economic fallout that came from it, people are fed up and broke. If the Liberal party doesn't find leadership who can tone down the nonsense they're going to get roasted in the next election, and that's not something that should really have happened at all except they have continued to double down on bad ideas for years.